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The Art
of Computer Game Design
by Cris Crawford

Preface to the Electronic Version This text was originally composed by computer game designer Chris Crawford in 1982. When searching for literature on the nature of gaming and its relationship to narrative in 1997, Prof. Sue Peabody learned of The Art of Computer Game Design, which was then long out of print. Prof. Peabody requested Mr. Crawford's permission to publish an electronic version of the text on the World Wide Web so that it would be available to her students and to others interested in game design. Washington State University Vancouver generously made resources available to hire graphic artist Donna Loper to produce this electronic version. WSUV currently houses and maintains the site. Correspondance regarding that site should be addressed to Prof. Sue Peabody, Department of History, Washington State University Vancouver, peabody@vancouver.wsu.edu. If you are interested in more recent writings by Chris Crawford, see the "Reflections" interview at the end of The Art of Computer Game Design. Also, visit Chris Crawford's webpage, Erasmatazz. This document was convert by Mario Croteau, from the Web site of the Department of History of Washington State University at Vancouver. Cris Crawford (the author) and Sue Peabody (of department of History of Washington State University at Vancouver) gave me a great support in my project: making that important document available to everyone.

The Art
of Computer Game Design
by Cris Crawford

Table of Contents Acknowledgement Preface Chapter 1 - What is a Game? BOARD GAMES CARD GAMES ATHLETIC GAMES CHILDREN’S GAMES COMPUTER GAMES REPRESENTATION Formal System Subjectively Represents Games versus Simulations Subset of Reality Summary of Representation INTERACTION Games versus Puzzles Games versus Stories Games versus Toys Significance of Interaction Nature of Interaction CONFLICT Games without conflict? Summary of Conflict SAFETY Summary of Safety Chapter 2 - Why Do People Play Games? Fantasy/Exploration Nose-Thumbing Proving Oneself Social Lubrication Exercise Need for Acknowledgement Summary MOTIVATION VERSUS SELECTION Game Play Sensory Gratification INDIVIDUAL TASTES Chapter 3 - A Taxonomy of Computer Games SKILL-AND-ACTION GAMES Combat Games Maze Games Sports Games Paddle Games 1 1 5 5 6 6 6 7 7 8 8 8 8 9 9 9 10 10 11 12 12 13 13 14 14 15 16 17 18 19 20 20 20 21 21 21 22 22 25 25 26 27 29 29

Race Games Miscellaneous Games TRATEGY GAMES Adventures D&D Games Wargames Games of Chance Educational and Children’s Games Interpersonal Games CONCLUSIONS Chapter 4 - The Computer as a Game Technology GAME TECHNOLOGIES COMPUTERS DESIGN PRECEPTS FOR COMPUTER GAMES Precept #1: GO WITH THE GRAIN Precept # 2: DON’T TRANSPLANT Precept #3: DESIGN AROUND THE I/O Precept #4: KEEP IT CLEAN Precept #5: STORE LESS AND PROCESS MORE Precept #6: MAINTAIN UNITY OF DESIGN EFFORT CONCLUSION Chapter 5 - The Game Design Sequence CHOOSE A GOAL AND A TOPIC RESEARCH AND PREPARATION DESIGN PHASE I/O Structure Game Structure Program Structure Evaluation of the Design PRE-PROGRAMMING PHASE PROGRAMMING PHASE PLAYTESTING PHASE POST-MORTEM Chapter 6 - Design Techniques and Ideals BALANCING SOLITAIRE GAMES Vast Resources Artificial Smarts Conclusions on Artificial Smarts Limited Information Summary RELATIONSHIPS BETWEEN OPPONENTS Symmetric Relationships Asymmetric Games Triangularity Actors and Indirect Relationships SMOOTH LEARNING CURVES THE ILLUSION OF WINNABILITY SUMMARY

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am deeply indebted to Madeleine M. Gross for her painstaking and thorough criticisms of this book. In many cases she invested greater efforts into her criticisms than I had put into my original thoughts. She strove to restrain my wild hyperbole and place my arguments on a

firmer foundation of rigorous logic. The logical consistency and reliability in this book I owe to her; the speculative flights of fancy must be laid at my doorstep.

The central premise of this book is that computer games constitute a new and as yet poorly developed art form that holds great promise for both designers and players. This premise may seem laughable or flippant. How could anybody classify the likes of SPACE INVADERS and PAC MAN as art? How can TEMPEST or MISSILE COMMAND compare with Beethoven’s Fifth Symphony, Michelangelo’s Pieta, or Hemingway’s A Farewell To Arms? Computer games are too trivial, too frivolous to be called art. They are idle recreation at best. So says the skeptic. But we cannot relegate computer games to the cesspit of pop culture solely on the evidence of the current crop of games. The industry is too young and the situation is too dynamic for us to dismiss computer games so easily. We must consider the potential, not the actuality. We must address the fundamental aspects of computer games to achieve a conclusion that will withstand the ravages of time and change. There are many definitions of art, few of which make much sense to the uninitiated. I will present my own pedestrian definition: art is something designed to evoke emotion through fantasy. The artist presents his audience with a set of sensory experiences that stimulates commonly shared fantasies, and so generates emotions. Art is made possible only by the richness of the fantasy world we share. Art is nevertheless difficult, because there are so many practical problems associated with stimulating fantasies deep inside another person’s mind. A major problem is getting the attention or participation of the audience. Most art allows very little participation. You sit quietly and listen to music that other people created and perform, or you stroll through a museum and stare at pictures or statues other people made. You sit passively and read a novel, or a poem, or a short story. With all of these art forms, the role of the audience is passive. The artist does all the active work, makes the biggest emotional investment. The audience is expected to absorb quietly the fruits of the artist’s exertions. Active participation is severely curtailed. Without participation, attention dwindles and impact crumbles away. This is in no wise a criticism of art or artists. The technologies of art preclude participation. If we had every klutz jump into the orchestra pit, or prance on the opera stage, or slop paint with

The Art of Computer Game Design


Picasso, we would have some great parties but no art. it seems the curse of art that artists can say so much in their work and most people will hear so little because they cannot participate in the art. Enter the computer. Conceived long ago, born in war, reared as the servant of business, this now adolescent technology has exploded out of the computer room and invaded shopping centers, pizza parlors, and homes. Popular characterizations of the computer alternate between the old image of the computer as omniscient, cold blooded, giant calculator, and the new image of the computer as purveyor of video thrills and 25 cent fixes. Originally developed as a number cruncher, the computer assumed a new personality when it was given graphics and sound capabilities. These capabilities gave the computer a powerful asset: it could now communicate with the human, not just in the cold and distant language of digits, but in the emotionally immediate and compelling language of images and sounds. With this capability came a new, previously undreamed of possibility: the possibility of using the computer as a medium for emotional communication art. The computer game has emerged as the prime vehicle for this medium. The computer game is an art form because it presents its audience with fantasy experiences that stimulate emotion. Unfortunately, the current generation of microcomputers cannot produce a sensory experience as rich as that produced by, say, a symphony orchestra or a movie. This weakness is more than offset by a fundamental advantage lacking in most other art forms: a game is intrinsically participatory in nature. The artist has here a tool that is more subtly indirect than traditional art. With other art forms, the artist directly creates the experience that the audience will encounter. Since this experience is carefully planned and executed, the audience must somehow be prevented from disturbing it; hence, non participation. With a game, the artist creates not the experience itself but the conditions and rules under which the audience will create its own individualized experience. The demand on the artist is greater, for s/he must plan the experience indirectly, taking into account the probable and possible actions and reactions of the audience. The return is far greater, for participation increases attention and heightens the intensity of the experience. When we passively observe someone else’s artistic presentation, we derive some emotional benefit, but when we actively participate in a game, we invest a portion of our own ego into the fantasy world of the game. This more sizable investment of participation yields a commensurately greater return of emotional satisfaction. Indeed, the role of participation is so important that many people derive greater satisfaction from participating in an amateur artistic effort than from observing a professional effort. Hence, games, being intrinsically participatory, present the artist with a fantastic opportunity for reaching people. Until now, games in general and computer games in particular have not been very impressive as art forms. The computer games especially are downright puerile. This is because the technology of computer games has been in the hands of technologists, not artists. These guys (and they are almost all male) can write beautiful operating systems, languages, linking loaders, and other technological wonders, but artistic flair has heretofore been treated as subordinate to technical prowess.

The Art of Computer Game Design


Another contributor to the fecklessness of our current computer games is the timidity of the marketplace. These machines are new; the public is unfamiliar with them and the manufacturers are hesitant to press the public too hard too fast. We therefore opt to build inhibited little games pathetically whispering some trivial emotion. Truly intense emotions or situations such as pathos, ecstasy, majesty, rapture, catharsis, or tragedy intimidate use. We hide behind the defense that we are in the entertainment business, not the art business, but that defense only betrays a profound misunderstanding of art. Art can be starchily elitist, but good art can also be a foot stomping blast. Elitism arises from the intellectual content of art; impact springs from its emotional honesty. Fortunately, times are changing. Already, we see a backlash developing against computer games. It expresses itself in many ways: in ordinances against the placement of arcade games in some areas, in statements by educators denouncing the games, and in more vigilant regulation of children’s game activities by parents. This backlash is viewed by smaller minded members of the industry with anxiety. More visionary thinkers watch the backlash with eager interest rather than defensiveness. The American people are telling us something here, something very important. It is imporant enough to them that they are willing to compromise their traditional reluctance to interfere with other people’s business. While the arguments presented in public debates normally focus on formal issues such as delinquency from school, creation of large groups of rowdy teenagers, and so forth, the concerns expressed privately reflect a distaste for the games, a vague suspicion that the games are a waste of time. You can’t fool all of the people all of the time; they are beginning to realize that the world of computer games is as yet a vast wasteland. Computer games are much like candy, comic books, and cartoons. All four activities provide intense or exaggerated experiences. Whether they use sugar, exclamation points, or animated explosions, the goal is the same: to provide extreme experiences. Children appreciate these activities because their novelty value is still strong. Adults, jaded by years of experience with such things, prefer diversions with greater subtlety and depth. We thus have the panoply of culinary achievement, the vast array of literature, and the universe of movies as the adult counterparts to candy, comic books, and cartoons. Yet, we have no adult counterpart to computer games. This deficit is pregnant with possibilities, for it suggests a momentous upheaval in computer game design. This developing revolution has nothing to do with the rapid technological developments of the last few years. While technological improvements will surely continue, we are no longer hampered primarily by the limitations of the hardware. Our primary problem is that we have little theory on which to base our efforts. We don’t really know what a game is, or why people play games, or what makes a game great. Real art through computer games is achievable, but it will never be achieved so long as we have no path to understanding. We need to establish our principles of aesthetics, a framework for criticism, and a model for development. New and better hardware will improve our games, but it will not guarantee our artistic success any more than the development of orchestras guaranteed the appearance of Beethoven. We are a long way from a computer game

The Art of Computer Game Design


comparable to a Shakespeare play, a Tchaikowsky symphony, or a Van Gogh self portrait. Each of these artists stood on the shoulders of earlier artists who plunged into an unexplored world and mapped out its territories so that later artists could build on their work and achieve greater things. We computer game designers must put our shoulders together so that our successors may stand on top of them. This book is my contribution to that enterprise.

The Art of Computer Game Design


CHAPTER ONE What is a Game?


f we desire to understand games and game design, we must first clearly establish our fundamental orientation. We must define what we mean by the word “game.” We must also determine the fundamental characteristics of all games. After discussing some of the obstacles

inherent in this effort, I will briefly describe the salient classes of games; then I will propose a set of attributes that characterize all games. Games are a fundamental part of human existence. The parlance of games has insinuated itself into our language to refer to activities that are not truly games. We play along with activities we find distasteful. We play ball with those who require our cooperation. We play games when we are insincere. A willing participant is game for the enterprise. This broad penetration of gaming concepts into the entire spectrum of human experience presents us with two potential barriers to understanding games. First, our liberal use of gaming terms promotes an exaggerated perception of our own understanding of games. We fail to render unto the subject the careful and critical analysis that we tender to more academic topics, and we blithely ignore the complexities of game design. Complete amateurs whose only relevant skill is programming undertake to design games with no further preparation than their own experience as game players. Those who overrate their own under-

standing undercut their own potential for learning. The second obstacle is ambiguity. We have applied the principles and concepts of gaming so widely that we have watered down their original meanings. There is no longer a clear focus to the concepts we seek to understand. Game designers have no well defined set of common terms with which to communicate with each other. Discussions of game design frequently disintegrate into arguments over semantics. To cut through the tangled undergrowth that has grown up around gaming we shall need the bulldozer and the scalpel. Let us begin this endeavor by stepping back for a moment and taking our bearings. Let us take a brief tour of the universe of games, glancing briefly at each of the major regions. In the course of this tour I hope to refresh the reader’s memory of games and make some simple points before digging into the serious analysis of fundamental game characteristics. I perceive five major regions of games: board games, card games, athletic games, children’s games, and computer games.

We begin with the board games. These games consist of a playing surface divided into sectors populated by a set of movable pieces. In the most common arrangement the pieces are directly associated with the players, while the playing surface represents an environment beyond the players’ direct control. Players maneuver their pieces across the playing surface in an effort to capture

The Art of Computer Game Design


other players’ pieces, reach an objective, gain control of territory, or acquire some valued commodity. The player’s primary concern in these games is the analysis of geometrical relationships between the pieces. Top

A second class of games is the card games. These games utilize a set of 52 symbols generated from two factors: rank (13 values) and suit (4 values). The games revolve around combinations built from these two factors. Players may gain or lose possession of symbols either by random processes or by matching some combination allowed by the rules of the game. Each legal combination is assigned a victory value for final assessment of game results. Players must recognize both existing and potential combinations and estimate probabilities of obtaining the cards necessary for completing a combination. This probability must be weighed against the victory value of the combination. Since the number of combinations is very large, precise computation of the requisite probabilities exceeds the mental powers of almost all players, rendering the game a primarily intuitive exercise. Thus, the player’s primary concern in these games is the analysis of combinations.

Another traditional game form is the athletic game. These games emphasize physical more than mental prowess. The rules of the game rigorously specify a precise set of actions that the player is either allowed to execute or required to execute. Skillful use of the body is the player’s primary concern in these .games. We must be careful to distinguish between athletic games and athletic competitions. For example, a race is a competition, not a game. The line of demarcation between games and competition illuminates one of the fundamental elements of all games. I distinguish the two by the degree of interaction between players. Theoretically speaking, the runners in a race do not interact with each other. Each is racing only against the clock; the presence of other runners should be immaterial. In truth, the runners do interact psychologically, for the performance of one runner can affect the performance of the other runners. Furthermore, in some races a runner (or driver or pilot or captain) can physically interpose himself in between the goal and another racer, thereby gaining an advantage. I conclude that the simplest competitions, those in which each person strives to perform some task optimally without direct interaction with the other competitors, do not constitute games but competitions. A competition that does allow interaction is a game. Top

Another type of gaming activity is the children’s game. Hide and Seek, Red Rover, Tag, and Kick the Can are common examples. Such games frequently take the form of group activities emphasizing simple physical play. Although these games contain simple mental and physical components,

The Art of Computer Game Design


their function is not to challenge the child to perform to his or her limits in either domain. Instead, the player’s primary concern in these games is the use of social skills illuminating the fundamental role of the group in human life. A wide variety of children’s activities are frequently referred to as games. When a child talks to a strip of bark, maneuvers it, and provides sound effects, we are tempted to refer to such behavior as game playing. For the purposes of this book, I ,exclude such activities from the fold of games. These improvisational games are too ill defined to provide us with any useful information about games. Top

The next area of gaming we shall glance at is the current fad in gaming and the subject of this book, the computer game. These games are played on five types of computers: expensive dedicated machines for the arcades (“coin op” machines), inexpensive dedicated machines (“hand helds”), multi program home games, machines such as the ATARI 2600 and the ATARI 5200, personal computers, and large mainframe computers. The computer acts as opponent and referee in most of these games; in many of them it also provides animated graphics. The most common form of computer game is the skill and action (“S&A”) game emphasizing hand eye coordination. These S&A games are frequently violent in nature. There are many other areas of computer gaming: adventure games, fantasy role playing games, and war games. In our cursory overview, these other computer games are eclipsed by the sheer volume of the skill and action games. This concludes our quick survey of the most prominent groupings in the universe of games. We shall return to the subject later, to create a taxonomy of computer games, and later still to draw on specific examples of games to make points about their nature. We must now address the question which motivated our initial reconnaissance: what are the fundamental elements common to these games? I perceive four common factors: representation, interaction, conflict, and safety.

First, a game is a closed formal system that subjectively represents a subset of reality. Let us examine each term of this statement carefully. By 'closed' I mean that the game is complete and self sufficient as a structure. The model world created by the game is internally complete; no reference need be made to agents outside of the game. Some badly designed games fail to meet this requirement. Such games produce disputes over the rules, for they allow situations to develop that the rules do not address. The players must then extend the rules to cover the situation in which they find themselves. This situation always produces arguments. A properly designed game precludes this possibility; it is closed because the rules cover all contingencies encountered in the game.

The Art of Computer Game Design


By formal I mean only that the game has explicit rules. There are informal games in which the rules are loosely stated or deliberately vague. Such games are far removed from the mainstream of game play.

The term 'system' is often misused, but in this case its application is quite appropriate. A game’s collection of parts which interact with each other, often in complex ways. It is a system.

Subjectively Represents
Representation is a coin with two faces: an objective face and a subjective face. The two faces are not mutually exclusive, for the subjective reality springs from and feeds on objective reality. In a game, these two faces are intertwined, with emphasis on the subjective face. For example, when a player blasts hundreds of alien invaders, nobody believes that his recreation directly mirrors the objective world. However, the game may be a very real metaphor for the player’s perception of his world. I do not wish to sully my arguments with pop psychological analyses of players giving vent to deep seated aggressions at the arcades. Clearly, though, something more than a simple blasting of alien monsters is going on in the mind of the player. We need not concern ourselves with its exact nature; for the moment it is entirely adequate to realize that the player does perceive the game to represent something from his private fantasy world. Thus, a game represents something from subjective reality, not objective. Games are objectively unreal in that they do not physically re create the situations they represent, yet they are subjectively real to the player. The agent that transforms an objectively unreal situation into a subjectively real one is human fantasy. Fantasy thus plays a vital role in any game situation. A game creates a fantasy representation, not a scientific model.

Games versus Simulations
The distinction between objective representation and subjective representation is made clear by a consideration of the differences between simulations and games. A simulation is a serious attempt to accurately represent a real phenomenon in another, more malleable form. A game is an artistically simplified representation of a phenomenon. The simulations designer simplifies reluctantly and only as a concession to material and intellectual limitations. The game designer simplifies deliberately in order to focus the player’s attention on those factors the designer judges to be important. The fundamental difference between the two lies in their purposes. A simulation is created for computational or evaluative purposes; a game is created for educational or entertainment purposes.(There is a middle ground where training simulations blend into educational games.) Accuracy is the sine qua non of simulations; clarity the sine qua non of games.

The Art of Computer Game Design


A simulation bears the same relationship to a game that a technical drawing bears to a painting. A game is not merely a small simulation lacking the degree of detail that a simulation possesses; a game deliberately suppresses detail to accentuate the broader message that the designer wishes to present. Where a simulation is detailed a game is stylized. Consider, for example, the differences between a flight simulator program for a personal computer and the coin op game RED BARON”. Both programs concern flying an airplane; both operate on microcomputer systems. The flight simulator demonstrates many of the technical aspects of flying: stalls, rolls, and spins, for example RED BARON has none of these. Indeed, the aircraft that the player files in RED BARON is quite unrealistic. It cannot be stalled, rolled, spun, or dived into the ground. When the stick is released it automatically rights itself. It is incorrect to conclude from these observations that RED BARON is inferior to the flight simulator. RED BARON is not a game about realistic flying; it is a game about flying and shooting and avoiding being shot. The inclusion of technical details of flying would distract most players from the other aspects of the game. The designers of RED BARON quite correctly stripped out technical details of flight to focus the player’s attention on the combat aspects of the game. The absence of these technical details from RED BARON is not a liability but an asset, for it provides focus to the game. Their absence from a flight simulator would be a liability.

Subset of Reality
The last term I use is “subset of reality.” One aspect of this term (“subset”) is easily justified. Clearly, no game could include all of reality without being reality itself; thus, a game must be at most a subset of reality. The choice of matter in the subset is the means of providing focus to the game. A game that represents too large a subset of reality defies the player’s comprehension and becomes almost indistinguishable from life itself, robbing the game of one of its most appealing factors, its focus.

Summary of Representation
A game creates a subjective and deliberately simplified representation of emotional reality. A game is not an objectively accurate representation of reality; objective accuracy is only necessary to the extent required to support the player’s fantasy. The player’s fantasy is the key agent in making the game psychologically real.

Some media for representing reality are static. A painting or sculpture depicts a snapshot of reality frozen in time. Some media are dynamic; they show change with time. Movies, music, and dance are dynamic in this way. They are able to represent the changing aspect of reality more richly. But the most fascinating thing about reality is not that it is, or even that it changes, but how it changes, the intricate webwork of cause and effect by which all things are tied together. The only

The Art of Computer Game Design


way to properly represent this webwork is to allow the audience to explore its nooks and crannies to let them generate causes and observe effects. Thus, the highest and most complete form of representation is interactive representation. Games provide this interactive element, and it is a crucial factor in their appeal.

Games versus Puzzles
One way to understand the nature of the interactive element of games is to contrast games with puzzles and other non interactive challenges. Compare playing a cube puzzle with playing a game of tic tac toe. Compare the sport of high jumping with the game of basketball. In each comparison the two activities provide similar challenges to the player. The key difference that makes one activity a game and the other activity not a game is the interactive element. A cube puzzle does not actively respond to the human’s moves; a high jump pole does not react to the jumper’s efforts. In both tic tac toe and basketball the opposing players acknowledge and respond to the player’s actions. The difference between games and puzzles has little to do with the mechanics of the situation; we can easily turn many puzzles and athletic challenges into games and vice versa. For example, chess, a game, has spawned a whole class of puzzles, the end game problems. Games can include puzzles as subsets, and many do. Most of the time the puzzles are a minor component of the overall game, for a game that puts most of its challenge value on included puzzles will rapidly lose its challenge once the puzzles have been solved.

Games versus Stories
Another way to illustrate the role of interaction is to compare games with stories. A story is a collection of facts in time sequenced order that suggest a cause and effect relationship. Frequently, the facts presented are deliberately fictitious, because the facts of a story are intrinsically unimportant. Indeed, the entire concept of fiction (“an untruth that is not a lie”) only makes sense when one realizes that the facts presented in the fiction are themselves unimportant. The cause and effect relationships suggested by the sequence of facts are the important part of the story. For example, we care not whether Luke Skywalker and the Death Star really existed. We saw that Luke Skywalker was good and pure, and that the Death Star was evil, and that Luke Skywalker destroyed the Death Star. The cause and effect relationship suggested by the story was that good overcomes evil. Thus, a story is a vehicle for representing reality, not through its facts per se, but through the cause and effect relationships suggested by the sequence of facts. Games also attempt to represent reality. The difference between the two is that a story presents the facts in an immutable sequence, while a game presents a branching tree of sequences and allows the player to create his own story by making choices at each branch point. The audience of a story

The Art of Computer Game Design


must infer causal relationships from a single sequence of facts; the player of a game is encouraged to explore alternatives, contrapositives, and inversions. The game player is free to explore the causal relationship from many different angles. Indeed, the player expects to play the game many times, trying different strategies each time. A story is meant to be experienced once; its representational value decreases with subsequent retellings because it presents no new information. A game’s representational value increases with each playing until the player has explored a representative subset of all of the branches in the game net. This does not mean that games are better than stories. Although stories trace only a single sequence of causal development, they do so with greater intricacy and detail than games. Detail is crucial to the creative success of a story, for it provides the texture, the feel of reality that makes a story compelling. The story writer unleashes a mighty swirling torrent of facts that sweeps the audience to its predestined conclusion. The game designer creates a complex network of paths cunningly crafted to show the player all possible facets of a single truth. In this respect, a story is like a statuette where a game is like a jewel. The statuette’s value arises from the fineness of detail and intricacy of construction. A jewel, by contrast, has no detail; its faces must be absolutely smooth. The jewel’s value arises from its ability to refract light into many different angles. A statuette is meant to be stationary; a jewel is meant to be moved. So too, is a story static where a game is dynamic. Stories enjoy a particular advantage over the current generation of computer games: the element of surprise. A good story boasts an array of interesting plot twists. The storyteller leads us into a set of expectations and then cleverly inserts a new factor that creates a disjunction, a new and dramatically different situation. This process can be repeated many times during the course of the story. Among computer games, only adventures provide this element of surprise. Unfortunately, the surprise can only be created by limiting the player’s freedom of action so as to guarantee that the player will encounter the surprise under the proper circumstances. After a while, all adventures begin to smell like primrose paths. The really exciting possibility offered by computer games is the prospect of formulating a plot twist in response to the player’s actions, instead of merely dragging him down a pre-ordained primrose path. However, the ability to formulate surprise requires an ability to analyze the player’s actions, deduce his expectations, and generate a believable plot twist that confutes his expectations without frustrating him. Artificial intelligence that advanced has yet to be created.

Games versus Toys
Games lie between stories and toys on a scale of manipulability. Stories do not permit the audience any opportunity to control the sequence of facts presented. Games allow the player to manipulate some of the facts of the fantasy, but the rules governing the fantasy remain fixed. Toys

The Art of Computer Game Design


are much looser; the toy user is free to manipulate it in any manner that strikes his fancy. The storyteller has direct creative control over his audience’s experience; the game designer has indirect control; the toymaker has almost none.

Significance of Interaction
Interaction is important for several reasons. First, it injects a social or interpersonal element into the event. It transforms the challenge of the game from a technical one to an interpersonal one. Solving a cube puzzle is a strictly technical operation; playing chess is an interpersonal operation. In the former, one plays against the logic of the situation; in the latter, one uses the logic of the situation to play against the opponent. Second, interaction transforms the nature of the challenge from a passive challenge to an active challenge. A puzzle will always present the player with exactly the same challenge. But a game opponent reacts to player’s actions, and presents different challenges in each game. This difference has major emotional significance. The person solving the puzzle must somehow divine, guess, deduce, master, or discover the key trick built into the puzzle by the designer. Emotionally, the puzzle player is working against the puzzle or its designer to unmask its secret. Once the secret is known, the puzzle is no longer interesting. The game-player, by contrast, faces different challenges each time she plays the game. Where a puzzle is dead a game is alive; the player must create her solution to the game in a manner best suited to her own personality and that of her opponent. The key distinction between a game and a puzzle is the difference between creating your own solution and discovering the designer’s solution. A game acknowledges the player’s existence and reacts to the player’s personality; a puzzle lies down like a dead fish. Computer games seldom provide a human opponent, and so they lack the social element that other games offer. They can, however, present an illusory personality against which the player must work. This is one of the most exciting and least developed potentials of the computer as a game technology. And regardless of the computer’s success or failure in synthesizing a social element, the computer can readily make the game a highly interactive experience for the player. It can react to the player’s moves with speed and thoroughness.

Nature of Interaction
Interactiveness is not a binary quantity; it is a continuous quantity with a range of values. Puzzles have little or no interactiveness, while games have more interactiveness. This suggests that interactiveness is an index of “gaminess”. Some games, such as blackjack, tag, or PONG provide very little interaction between the players. Although the players may wish to interact, the games provide very limited modes of interaction (binary decision to stand or hit, running, and twisting paddle). The games do not allow players to invest much of themselves into the play, or to react in a rich way to their opponents. Other games, such as bridge, football, and LEGIONNAIRE (trademark of Avalon Hill Game Co.) allow a far richer interaction between players. Players can grap-

The Art of Computer Game Design


ple with each other at a variety of levels. The first group of games is generally acknowledged to be dull, while the second group of games is generally regarded as more interesting. What is important about the modes of interaction is not their mechanical quality but their emotional significance. PONG is insipid because I can’t express much of my personality through the medium of a bouncing ball. Bridge is better because it includes within its interaction elements of teamwork, deception, and cooperation. I can better imprint my personality traits onto a game of bridge. Thus, degree of interaction provides a useful index of “gaminess”. Top

A third element appearing in all games is conflict. Conflict arises naturally from the interaction in a game. The player is actively pursuing some goal. Obstacles prevent him from easily achieving this goal. If the obstacles are passive or static, the challenge is a puzzle or athletic challenge. If they are active or dynamic, if they purposefully respond to the player, the challenge is a game. However, active, responsive, purposeful obstacles require an intelligent agent. If that intelligent agent actively blocks the player’s attempts to reach his goals, conflict between the player and the agent is inevitable. Thus, conflict is fundamental to all games.

Games without conflict?
Some people shrink’ from this aspect of games. A number of attempts have been made to design “nice” games cleansed of conflict. Such games emphasize cooperative efforts rather than conflict. They have not been successful commercially; this suggests that few people enjoy them. More importantly, these games are failures because they are not games in the first place. Conflict can only be avoided by eliminating the active response to the player’s actions. Without active response, there can be no interaction. Thus, expunging conflict from a game inevitably destroys the game. While it is impossible to eliminate conflict from a game without destroying the game, it is possible to include cooperative elements by shifting the conflict. Members of a team can cooperate with each other in the team’s conflict with another agent. This other agent could be another team, an individual human, or a computer simulated player. In all cases, the opponent must be perceivable as endowed with a persona. Without at least the illusion of purposeful reaction to the player’s actions, the game collapses. This “blood and guts” view of conflict in games is reinforced by the social context in which they are often played. Our real world conflicts are always indirect, diffused over time, and tightly regulated. Moreover, they all too frequently lack resolution, for seldom does one achieve an outright victory in the conflicts of daily life. Local successes, yes, but the struggle continues without clear resolution. Because games are subjective representations of the real world, they focus our attention on a particular aspect of the world by accentuating that aspect. Conflict in games thus tends

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to be (but need not always be) accentuated to its most direct and intense form violence. Violence is not essential or fundamental to games. It is common in games because it is the most obvious and natural expression for conflict.

Summary of Conflict
Conflict is an intrinsic element of all games. It can be direct or indirect, violent or nonviolent, but it is always present in every game. Top

Conflict implies danger; danger means risk of harm; harm is undesirable. Therefore, a game is an artifice for providing the psychological experiences of conflict and danger while excluding their physical realizations. In short, a game is a safe way to experience reality. More accurately, the results of a game are always less harsh than the situations the game models. A player can blast the monsters all day long and risk only her quarter. She can amass huge financial empires and lose them in an hour without risking her piggy bank. She can lead great armies into desperate battles on which hang the fate of nations, all without shedding a drop of blood. In a world of relentless cause and effect, of tragic linkages and inevitable consequences, the disassociation of actions from consequences is a compelling feature of games. This is not to imply that games are devoid of consequences. The penalties for losing a game can sometimes be a significant deterrent to game play. Losing to another person always entails some loss of dignity. This may be an attraction of computer games there is less shame in losing to a computer. The loser can keep coming back for more defeats without losing face. Moreover, true victory the total destruction of the computer’s forces, is acknowledged to be impossible in most such games; this further lessens the shame of defeat. A second penalty for losing is the less of any reward that might have been gained by winning. In almost all games the reward penalty structure is positive. That is, the loser is not punished for losing, the winner is rewarded for winning. The loser’s only loss is any investment that he made to enter the game, such as a bet or entry fee. This investment is usually very small, and may rightly be regarded as a recreational fee for the services associated with the administration of the game rather than a penalty for all potential losers. Gambling presents us with some difficult problems related to the issue of the safety of games. Gamblers risk money or goods on the outcome of a random or near random process. Losers forfeit their bets and winners reap a large reward. Hence, gambling presents a real financial risk to the player. However, two extenuating circumstances intervene: first, the recreational gambler risks very little money; second, some gamblers deny to themselves the laws of chance. They indulge in the fantasy of control. The proper intonation in the shake of the dice, the correct twist on the handle of the slot machine these things make the difference, or so they tell themselves. Thus, recreational gambling, while somewhat deviant from the mainline of game playing, probably deserves

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inclusion in the fold of games. Serious gambling, however, involving large sums of money expended more for anticipated financial gain than for recreation, lies on the far side of the gray zone. A special form of gambling, deserving special consideration here, is poker. Poker is a game of bluffing; the key to success in the game lies in convincing your opponent that you have better or worse cards than you really have. Because money is at stake, the player experiences stresses that strain his ability to deceive his opponents. Thus, the risk of gambling, a mere outcome of other games, is an intrinsic part of the structure of poker. This unique aspect of poker merits special consideration. I would not hesitate to classify poker as a game.

Summary of Safety
Games provide safe ways to experience reality. Special cases abound, but the central principle remains: games are safe. In this chapter I have presented a set of characteristics that defines what I mean by the word “game”. For the most part, I have emphasized the characteristics intrinsic to the games themselves rather than the motivations of the players. Such separation of game from player is artificial and misleading, for neither exists without the other. In the next chapter, I turn to look at the players of games and their motivations.

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Chapter Two Why Do People Play Games ?


ame-playing requires two components: a game and a player. The game designer works to produce a game, and so her immediate preoccupation is with the game itself. Yet, her final goal is to educate, entertain, or edify the game-player; hence, the human player is

the proper primary concern of the game designer. Why do people play games? What motivates them? What makes games fun? The answers to these questions are crucial to good game design. One way to address the question of the purpose of games is to inquire into their history. Games now are too varied, too intricate, too involved, to indicate a single clear function. Perhaps their fundamental nature would be more evident in their earliest incarnations. How far back must we go? To MONOPOLY, created during the Depression? No, card games were played long before that. Indeed, the discoverers of King Tutankhamen’s tomb found among the wealth there a wooden surface with regular divisions that appears to be some sort of boardgame. But even archaeology does not take us far enough back. If we wish to get back to the beginnings of games, we must go beyond the realm of the archaeologist and into the realm of the paleontologist. We must reach not thousands but millions of years into the past to find the earliest games, for games predate not just history but all of mankind. They are not a human invention. Fortunately, direct recourse to paleontology is unnecessary. A trip to the zoo will suffice. There we find two lion cubs wrestling near their mother. They growl and claw at each other. They bite and kick. One cub wanders off and notices a butterfly. It crouches in the grass, creeps ever so slowly toward its insect prey, then raises its haunches, wiggles them, and pounces. We laugh at the comedy; we say that the cubs are playing a game, that they are having fun, and that they are such funloving, carefree creatures. We are right on the first count: these cubs do indeed appear to be playing a kind of game. We can certainly see in their behavior all four of the fundamental game attributes described in Chapter 1: representation, interaction, conflict, and safety. We may be right on the second count; who knows if lions can have fun? But we are dead wrong on the last count. These cubs are not carefree. They do not indulge in games to while away the years of their cubhood. These games are deadly serious business. They are studying the skills of hunting, the skills of survival. They are learning how to approach their prey without being seen, how to pounce, and how to grapple with and dispatch prey without being injured. They are learning by doing, but in a safe way. Better to make mistakes with butterfly and sibling than with the horns of the wildebeest. Games are thus the most ancient and time-honored vehicle for education. They are the original educational technology, the natural one, having received the seal of approval of natural selection. We don’t see mother lions lecturing cubs at the chalkboard; we don’t see senior lions writing their memoirs for posterity. In light of this, the question, "Can games have educational value?" becomes absurd. It is not games but schools that are the newfangled notion, the untested fad, the violator of tradition. Game-playing is a vital educational function for any creature capable of learning.

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The incidence of game-playing in animals is itself instructive. Game-playing has been observed only in mammals and birds. The phylogenetically earlier orders (fish, insects, amphibians, and reptiles) have not been shown to engage in game-playing. (See Animal Play Behavior, by Robert Fagen, Oxford University Press.) Game play seems to be associated with that quality which we have clumsily attempted to measure with brain size, intelligence, and ability to learn. This correspondence cannot be attributed to accident; clearly game play is an important component in the development of many creatures. We commonly associate the playing of games with children. Indeed, "play" as an activity is considered to be the almost exclusive preserve of children, and the term is applied to adults either disparagingly or jocularly. Children are expected to play games because we recognize (perhaps unconsciously) the fundamental utility of games as an educational tool. As children grow up, cultural pressures change and they are encouraged to devote less time to the playing of games so that they can devote themselves to more serious activities. I claim that the fundamental motivation for all game-playing is to learn. This is the original motivation for game-playing, and surely retains much of its importance. This claim does not conflict with my other primary assertion that computer games constitute a new art form. Consider, for example, humans and food. The fundamental motivation to eat food is the base desire for nourishment, yet this has not prevented us from embellishing this fundamental activity with all manner of elaborate and non-nourishing customs, rituals, seasonings, and garnishes. I do not mean to imply that food is an art form; only that we humans can take an activity far beyond its prime cause without denying that prime cause. I must qualify my claim that the fundamental motivation for all game-play is to learn. First, the educational motivation may not be conscious. Indeed, it may well take the form of a vague predilection to play games. The fact that this motivation may be unconscious does not lessen its import; indeed, the fact would lend credence to the assertion that learning is a truly fundamental motivation. Second, there are many other motivations to play games that have little to do with learning, and in some cases these secondary motivations may assume greater local importance than the ancestral motivation to learn. These other motivations include: fantasy/exploration, nose-thumbing, proving oneself, social lubrication, exercise, and need for acknowledgment. I shall examine each in turn.

A very important motivation to play games is fantasy fulfillment. Like a movie, a book, or music, a game can transport the player away from the tawdry world that oppresses him and create a fantasy world in which he can forget his problems. Games are potentially superior to the traditional means of escape (movies, books, music) because they are participatory. Instead of merely watching

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a movie reading a book, or listening to music, the player is actively involved in the game. Indeed, the player drives the game, controls it in a way that is quite impossible with the passive fantasies. This need to escape, to fantasize is certainly an important motivation. Fantasy fulfillment frequently takes the form of symbolic exploration. There’s a big world out there, full of exciting things, people, and places, yet most of us are confined to a world ,of asphalt, plastic, and paper. Many art forms attempt to transport the audience into a different world, to present experiences or feelings not often known in the everyday world. Consider, for example, the success of Disneyland. This place is undoubtedly the most successful of its genre. Such parks are often called "amusement parks" or "theme parks." These terms are misleading, for the success of Disneyland cannot be attributed solely to its amusements and diversions. These elements are technically excellent, but other amusement parks sport technically excellent rides. The success of Disneyland can be summed up in one word: fantasy. Disneyland creates and supports an aura of fantasy, a context of make-believe that permeates all of the activities within the park. Within moments of entering the park, the visitor feels that s/he is in a different world. Fanatic attention to detail in signposts, walls, windows, even railings has created an environment that encourages suspension of disbelief. Fantasy is an important component of human play. It is critical to our recreation, our art and our games.

A common function of games is to provide a means of overcoming social restrictions, at least in fantasy. Many games place the player in a role that would not be socially acceptable in real life, such as a pirate or a thief. An excellent (albeit extreme) example of this is the game CRUSH, CRUMBLE, AND CHOMP by Automated Simulations. In this game the player is cast as a 1950’svintage monster going on a rampage through his favorite city. He stomps on police cars, crushes buildings, swats helicopters, and creates general mayhem. The box art shows a monster about to attack an IRS building as terrified citizens flee. This represents an extreme case of anti-social behavior made acceptable by the safety of the game. Sometimes the player’s role is itself socially acceptable, but the actions taken are discouraged in real life. MONOPOLY encourages players to engage in what the Federal Trade Commission delicately calls "predatory trade practices." Wargames encourage players to start and win wars. Some games address sexual matters, allowing players to indulge in make-believe behavior that they could never exhibit in the real world. The most telling example of this nose-thumbing phenomenon lies in the arcade games. These games emphasize violence, and lots of it. The theme is almost universal in arcades: destroy somebody. The coup de grace is not delivered discreetly or elegantly. On the contrary, the victim is dispatched with the most colorful animated explosion possible. Like a Sam Peckinpah movie,

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the violence is the whole point and purpose of the enterprise. Yet, even as we pander to these distasteful emotions, we delicately mask them in less offensive garb. We never, never obliterate human beings; instead, we vaporize ugly space monsters. The monsters have perpetrated some odious interstellar crime, so the player is cast as the defender, the protector, or the avenger. The case is often presented that the game represents a time of extreme crisis ("THE FATE OF HUMANITY IS AT STAKE!!!"). This heightens the player’s sense of urgency; it also conveniently justifies the use of extreme violence, thereby allowing the player to have violence without guilt. The player can thumb his nose at social strictures and engage in violence and mass murder without risking censure. The game provides a safe way to thumb one’s nose.

Proving Oneself
Another function of games is as a means of demonstrating prowess. All games support this motivation to a greater or lesser degree. Many game-playing communities sponsor tournaments or player ratings. Arcade games support this function by recording and displaying the initials of the top-scoring players. There are also players who carry this to extremes. Their prime goal is not merely to win, but to beat somebody, preferably somebody worth beating. Chess has an unusually high concentration of such sharks; so do wargames. A common question asked during a wargame is "Are you playing for blood or for fun?" Such players normally prefer games that allow their skill to be properly brought to bear, so they tend towards games in which chance plays a minimal role. Despite this concentration of such players in deductive logic games, almost all games have sharks preying on the playful players. When a shark plays for serious rewards (e.g., social dominance) and -takes serious risks of failure, the crucial element of safety is eliminated from the game, and the game ceases to be a game; it becomes a conflict. Inasmuch as all games have the potential for being played in an overly competitive way, some people who are especially sensitive to the social risks of game-as-conflict refuse to play games, for they do not perceive the games to be safe. If they do play, they prefer to play games of pure chance, not so much to disable or discourage the shark as to create a situation in which winning is patently unrelated to prowess. If winning is arbitrary, social risk is eliminated and safety is restored. It is impossible to design a game that is unalterably safe (i.e., invulnerable to sharks) without resorting to pure chance as the sole determinant of victory. If the game in any way allows individual prowess to affect the outcome, then the outcome is perceivable as a reflection of individual prowess. In most games, safety from social risk is conferred onto the game by the attitudes of the players, the willingness to say, "It’s only a game."

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Social Lubrication
Games are frequently used (especially by adults) as social lubricants. The game itself is of minor importance to the players; its real significance is its function as a focus around which an evening of socializing will be built. Card games and some light board games serve this function. An excellent example of such a social lubricant game is a game utilizing a large plastic gameboard about four feet square that is marked with colored spots. On each player’s turn, a random process is used to determine which of four appendages (arms or legs) is to be placed on which spot on the board. As the players contort to fulfill the game requirements, they inevitably make physical contact with each other in innocent and foolishly humorous ways. Social interaction is thereby fostered.

Exercise is another common motivation to play games. The exercise can be mental or physical or some combination of both; in either event, the game is an entertaining way to stay in shape. Some players like to exercise their cognitive skills, while others prefer the use of intuition. Some players prefer to exercise their athletic skills. Furthermore, players need to exercise their skills at an appropriate level. A chess player will get very little exercise out of a game of tic-tac-toe. Similarly, a person who finds tic-tac-toe challenging will get little useful exercise out of chess. These preferences sort players out and route them to the different games available.

Need for Acknowledgment
We all need to be acknowledged, to be recognized by other people. The acknowledgment we crave is not merely an acknowledgment of our existence, but of our personalities. For example, when we meet a casual acquaintance, we usually get a perfunctory acknowledgment ("Hello there, Jones.") We are more gratified when the greeting in some way acknowledges us as individuals with special personalities and problems ("Hello there, Jones; is that knee still bothering you?") The popularity of pets provide another example of the need for acknowledgment. Why on earth do we keep in our homes animals that require food, veterinary attention, and sanitary maintenance? Because they acknowledge us. We can interact with pets; we talk to them, play with them, and emote with them. A dog is an especially responsive creature; it can read our facial expressions and interpret our tone of voice. A smile will trigger tall-wagging; a kind word will precipitate jumping, licking, barking, or some other expression of affection. Goldfish, by contrast, neither appreciate nor express emotion. Thus, even though goldfish are much easier to care for, most people prefer dogs as pets. People value acknowledgment enough to expend the effort to obtain it. This is one reason why interaction is so important to a game; it allows the two players to acknowledge each other. A truly excellent game allows us to imprint a greater portion of our personalities into our game-playing. Such a game allows me to play in a way that only I could have played it.

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My opponent must look beyond the playing pieces and acknowledge my cleverness, my rashness, my deviousness, my entire personality. When such a game ends, my opponent and I know each other better than we did before we sat down to play.

Many factors play a role in motivating a person to play a game. The original (and almost instinctive) motivation is to learn, but other motivations come to bear as well. Top

We must be careful to distinguish between factors that motivate people to play games in the first place and factors that allow people to choose between games. In other words, the answer to the question, "Why do people play games?" can be quite different from the answer to the question, "What makes one game more fun than another?" Some factors motivate a person to play games; other factors help that person select a particular game. For example, sensory gratification is such a selection factor. A player who has decided to play a particular type of game will prefer a game with excellent graphics over games with poor graphics; yet the graphics alone will not motivate many people to play games. Motivating factors get people to approach games in general; enjoyment factors help them make their choice of particular games. Distinguishing motivation from enjoyment is not tantamount to denying correlation’s between motivating factors and enjoyment factors. Clearly, any game that does not deliver the experiences implied by the motivating factor will not be enjoyed. Thus, some (but not all) motivating factors will also be used as enjoyment factors. If a player is motivated to play a game for mental exercise, that player will probably prefer those games that offer better mental exercise than do other games. A game cannot be fun if its factors do not satisfy the motivations of the player. Two enjoyment factors that are not in themselves motivational are game play and sensory gratification. Top

Game Play
Game play is a crucial element in any skill-and-action game. This term has been used for some years, but no clear consensus has arisen as to its meaning. Everyone agrees that good game play is essential to the success of a game, and that game play has something to do with the quality of the player’s interaction with the game. Beyond that, nuances of meaning are as numerous as users of the phrase. The term is losing descriptive value because of its ambiguity. I therefore present here a more precise, more limited, and (I hope) more useful meaning for the term "game play". I suggest that this elusive trait is derived from the combination of pace and cognitive effort required by the game. Games like TEMPEST have a demonic pace, while games like BATTLEZ0NE have a far more deliberate pace. Despite this difference, both games have good game play, for the pace is appropriate to the cognitive demands of the game. TEMPEST requires far less planning and conceptualization than BATTLEZONE; the demands on the player are simple and direct, albeit at a

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fast pace. BATTLEZONE requires considerably greater cognitive effort from the player, but at a slower pace. Thus, both games have roughly equivalent game play even though they have very different paces. Pace and cognitive effort combine to yield game play.

Sensory Gratification
Sensory gratification is another important enjoyment factor. Good graphics, color, animation, and sound are all valued by game players. They support the fantasy of the game by providing sensory "proof" of the game’s reality. We see a related phenomenon in the movies: special effects. Some of the newer movies have excited great interest because of the excellent special effects they utilize. These movies have placed us in the thick of space battles, let us meet strange and wonderful creatures, and taken us to faraway places. The things we see look so real that we believe the fantasy; we know (subjectively) that the fantasy is real. Similar processes can be applied to games. Special effects, graphics, sound, animation-these factors all help distinguish a good game from a bad game. We must not confuse their role, however; sensory gratification is a crucial support function, not a central feature. Sensory texture enhances the impact of the fantasy created by the game or movie, but wonderful graphics or sound do not by themselves make the product. A movie without a believable or enjoyable fantasy is just a collection of pretty pictures; a game without an entertaining fantasy is just a collection of interactive pretty pictures.

So far I have discussed motivational and enjoyment factors as if they were absolute quantities whose significance is independent of the individual player. Such is not the case; the response to a given game depends heavily on the personality of the prospective player. How are we to deal with the personality differences that dominate the individual's response to games? One academic solution to this problem is to postulate the existence of a very large number of personality traits that determine the individual response to a game. We next postulate a like number of game traits that, taken together, completely define the psychological profile of the game. Next, we measure and catalog all of the personality traits of any given individual, presumably with an omniscient "personalitometer". Then we measure all the game traits of the game in question with an equally powerful "gamometer". We then perform a matrix multiplication of personality traits against game traits. Sometime before the sun enters its red giant phase, our monster computer returns a number telling us how much that person will enjoy that game. This approach will for the moment remain a gedanken-experiment. We must devise simpler, admittedly less reliable means of coping with individual differences. One alternative route is to observe and catalog groups of game-players, and identify the game traits valued by these groups. This method is made difficult by the youth of the computer game

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industry. We can at this time identify only a few broad, vague, and overlapping groups of players: skill-and-action enthusiasts, D&D enthusiasts, and strategy gamers. There remain several other game types, but they have not attracted so large a following as to present us with a definable group of players. The passage of time and further research will certainly give us more information with which to work. Individual tastes in games are not static; as a person changes so do the tastes. The following analogy with music illustrates this point. As children, we are all exposed to music in a variety of forms, but it has little impact on us because our tastes are poorly developed. We sing and dance to simple songs, but a full appreciation of the emotional range of music eludes us. The power of music arises from our ability to associate musical expressions with emotions. It takes years to develop these associations, and they are made in the context of our experiences. For many in my generation, the first deep contact with music came with rock 'n roll in the 60’s. The pounding beat, simple themes, and short durations were easily grasped by our adolescent and unsophisticated minds. We could understand this music. Moreover, the act of listening to and enjoying this music was itself an educational experience. As the range of our musical experience expanded, we learned more complex components of the musical lexicon and developed a wider range of associations. Soon we were able to understand and appreciate other musical compositions previously inaccessible to our untrained ears. Rock music changed to reflect this maturation; some of us stayed with rock. Others moved to jazz, country, or folk. Like some others, I moved from rock to classical in a series of stages. As I moved along this evolutionary path, the lessons of one stage enabled me to understand the material of the next stage. Other people followed their own paths, exploring and learning the areas of musical expression that most appealed to them. The common experience was that our musical tastes evolved, no matter what direction we chose. Rock music was the broad base we all shared, the entry point or ,junk out of which sprang many branches. Just as rock 'n roll was the entry point into the world of music for an entire generation, so will skill-and-action games be the entry point into the world of games for the whole population. Like early rock 'n roll, skill-and-action games have broad appeal, and are easy to understand. As people become more sophisticated with games, their tastes will evolve down different branches. Like rock 'n roll, skill-and-action games will not go away; they will change to reflect the evolving taste of the public. We can see this happening already. The early arcade games are tame pussycats compared to the rip-snorting, fire-breathing games of 1982. Had TEMPEST been released in 1977, it would have intimidated and repelled players. Times change; people change. Skill-and-action is here to stay and will always provide an entry point for new players, but the public will not stand still. Many people will move on to explore other areas of game-playing.

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People play games for many reasons. In this chapter, I have touched on a variety of these motivations. I readily admit that my treatment of the subject matter is thin, speculative, and uncompelling. People are complex creatures; we will never fully understand human motivations to play games. Yet me must appreciate the importance of these motivations and at least try to understand them if we are to master the art of computer game design.

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CHAPTER THREE A Taxonomy of Computer Games


housands of computer games are commercially available on a variety of hardware configurations. These games present a bewildering array of properties. Many show close similarities. Most possess some unique design feature. Given this large sample of games, we can

learn a great deal about game design by establishing a taxonomy of computer games. A taxonomy would illuminate the common factors that link families of games, while revealing critical differences between families and between members of families. A well-constructed taxonomy will often suggest previously unexplored areas of game design. Most important, a taxonomy reveals underlying principles of game design. In another field of study, Charles Darwin’s meticulous taxonometric work while on the Beagle led almost inevitably to his development of the theory of evolution. While we cannot hope that taxonometric work in computer game studies will be so spectacularly productive, it certainly seems worth the effort. I will insist on an important qualification: I do not claim that the taxonomy I propose is the correct one, nor will I accept the claim that any correct taxonomy can be formulated. A taxonomy is only a way of organizing a large number of related objects. If there were some organizing agent, some underlying process that created the group of objects, then we could reasonably expect to be able to find a single correct taxonomy embodying the central organizing principle in its structure. For example, the wide array of living creatures on this earth did not arise by chance; this array is the product of natural selection. Natural selection is a reasonable, understandable, nonarbitrary process. Therefore, there is only one reasonable taxonomy for life on earth, the taxonomy that embodies the principles of natural selection. In the shape of an airplane we can see the principles of aerodynamics; so too in a taxonomy of living creatures can we see the hand of natural selection. Such is not the case with computer games. The field is too young, the sample too small, for whatever organizing principles there may be to have asserted themselves. The games we now have are more the product of happenstance than the inevitable result of well-established forces. Without a wide array of games there is little opportunity to choose between games; without choice there can be no natural selection. It is therefore impossible for us to devise a single, absolute taxonomy. Many taxonomies are admissible. Indeed, attempting to construct several alternative taxonomies is a useful way to examine the common traits of computer games. I am not so ambitious; I shall be happy to propose just one taxonomy. I divide computer games into two broad categories: skill-and-action ("S&A") games (emphasizing perceptual and motor skills) and strategy games (emphasizing cognitive effort). Each major category has several subcategories. Top

This is easily the largest and most popular class of computer games. Indeed, most people associate all computer games with skill-and-action games. All arcade games are S&A games and almost

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all games for the ATARI 2600 are S&A games. This class of games is characterized by real-time play, heavy emphasis on graphics and sound, and use of joysticks or paddles rather than a keyboard. The primary skills demanded of the player are hand-eye coordination and fast reaction time. I group skill-and-action games into six categories: combat games, maze games, sports games, paddle games, race games, and miscellaneous games. Top

Combat Games
Combat games all present a direct, violent confrontation. The human player must shoot and destroy the bad guys controlled by the computer. The challenge is to position oneself properly to avoid being hit by the enemy while shooting him. These games are immensely popular; they are Atari’s forte. There are many variations on this theme, most arising from variations on the geometry of the situation or the weaponry of the opponents. STAR RAIDERS and SPACEWAR can be compared on these bases of geometry and weaponry. In both games the player files through space in a rocket ship and engages enemy spaceships in realtime cosmic dogfights. STAR RAIDERS presents the conflict in first-person geometry (that is, the television screen shows the same scene that the pilot would see.) SPACEWAR uses much the same weaponry and mechanisms with one crucial difference: the geometry of the game is third-person rather than first-person (that is, the player sees his own and his opponent’s spaceships from a distance.) The difference in result is obvious to anyone who has played both games. The first-person game is more exciting and compelling than the third-person game. Unfortunately, the first-person geometry is so technically difficult to execute that it has been implemented on only a few games. Most games use third-person geometry. ASTEROIDS is a shoot-em-up game that uses the same space environ that STAR RAIDERS uses. The primary difference between the two games is in the nature of the opposition. The enemy in ASTEROIDS is not a small number of intelligent opponents armed with weapons identical to the player’s; instead, the enemy is a large number of stupid rocks armed only with their ability to destructively collide with the player. MISSILE COMMAND is another combat game with several interesting twists. First, the player must defend not only himself but also his cities from descending nuclear bombs. Second, the game is a purely defensive game in that the player never has the opportunity to attack his enemy. Third, while shots in other games are very rapid events, the shooting process in this game is slower and takes time to develop because the missiles must fly to their targets before detonating. Because the time between firing and impact is so long, the player must plan his shots with greater foresight and make use of multiple explosions. Thus, although this is a skill-and-action game, there are more strategic elements involved than in many games of this category. SPACE INVADERS (trademark of Taito America Corp.) is one of the most successful combat games of all time. It was one of the first smash hit games and contributed to the upsurge of pop-

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ularity of computer games that began in 1979. While STAR RAIDERS and ASTEROIDS give the player great mobility and MISSILE COMMAND gives him none, SPACE INVADERS gives the player limited mobility in one dimension only. As in ASTEROIDS, the player must face a multitude of rather stupid opponents who can win by touching the player (landing); in addition, as in STAR RAIDERS, the monsters also shoot back. The monsters march back and forth across the screen, slowly descending onto the player. As the player kills more and more monsters, they march faster and faster. This gives the game a hypnotic accelerating tempo. SPACE INVADERS is definitely a classic. The success of SPACE INVADERS has spawned a whole series of copies and derivatives. There are a large number of copies whose only goal was to cash in on the success of the original game. There are also several genuine derivative games. For example, GALAXIAN (trademark of Midway) is a simple variation on SPACE INVADERS. Individual invaders peel off and attack the player with more ferocity than the docile monsters of the original game. CENTIPEDE; is also a derivative of SPACE INVADERS; it is different enough to be a new design, but the internal game structure is very similar to the original. The invaders have been grouped into a segmented centipede; their side-to-side motion is bounded not by the edges of the screen but by mushrooms randomly scattered across the screen. Numerous embellishments (spiders, fleas, and scorpions) extend the game considerably. TEMPEST is a three-dimensional first-person derivative of SPACE INVADERS using vector graphics. The amount of design attention that SPACE INVADERS has attracted is a tribute to the game’s originality, appeal, and durability There are many, many other combat games. BATTLEZONE and RED BARON are two first-person combat games utilizing vector displays. Other combat games include CAVERNS OF MARS, YAR’S REVENGE, CROSSFIRE (trademark of On-Line Systems) and DEFENDER (trademark of Williams). You may wonder why so many combat games are set in outer space. There are three reasons. First, space is easy to depict and animate with a computer---all the designer need do is draw a blank screen with a few white dots for stars. Second, space is not encumbered by the expectations of the players. A designer encountering problems can always concoct some super-duper zapper to solve any design problems with the game and nobody can object that it is unrealistic. Earthbound games constrain the designer to look reality squarely in the eye---such a tiresome burden for a "creative" mind. Third, space is an intrinsically fantasy-laden environment that encourages suspension of disbelief because it is unfamiliar to its audience. Combat games have always been at the heart of computer gaming. Players never seem to tire of them; it appears that they will be around for a long time to come.

Maze Games
The second subgrouping of S&A games is the set of maze games. PAC-MAN (trademark of Namco) is the most successful of these, although maze games predate PAC-MAN. The defining

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characteristic of the maze games is the maze of paths through which the player must move. Sometimes one or more bad guys pursue the player through the maze. Some maze games (MAZE CRAZE for the ATARI 2600 is a good example) specifically require that the player make his way to an exit. Other maze games require that the player move through each part of the maze. DODGE 'EM is an early example of such a game. In either case, the number, speed, and intelligence of the pursuers then determines the pace and difficulty of the game. PAC-MAN has a very carefully balanced combination of these factors. The pursuers are just slightly slower than the human player; their intelligence and number make up for this. The overall pace of the game makes it difficult for the player to fully analyze the positions of the five pieces in real time. Any successful game is certain to attract copies, variations, and derivatives, and PAC-MAN is no exception. One of the first such games for the ATARI Home Computer System was the first edition of JAWBREAKERS (trademark of On-Line Systems). This game, now removed from the market, clearly demonstrates the difference between structural changes and cosmetic changes. Structurally, it is indistinguishable from PAC-MAN. The play of the game is almost identical to that of PAC-MAN. Cosmetically, there are a number of differences: the pursuers are faces rather than ghosts; the player is a set of teeth rather than a head with mouth; the maze is laid out differently; the sounds are different. This game provides a good example of the methods that can be used to copy games while attempting to minimize legal problems. Another PAC-MAN derivative is MOUSKATTACK (trademark of On-Line Systems). This game shows some structural changes relative to PAC-MAN. The player is again pursued through a maze by four computer-controlled creatures, but the basic scenario contains a number of embellishments. First, merely passing through every point in the maze is not enough; some points, randomly chosen by the computer, must be passed through twice. Second, the player is allowed to fight back against the pursuers in a very different way (setting mousetraps). The strategic and tactical effects of this counterforce capability yield a game that plays rather differently. Finally, there is a very interesting two-player game that allows both cooperative and competitive strategies. In MOUSKATTACK we see the basic structure of PAC-MAN with a number of embellishments and extensions that produce a distinct game. The appeal of maze games can be attributed to the cleanliness with which they encapsulate the branching structure that is a fundamental aspect of all games. The reader will remember from Chapter One that a game has a tree structure with each branch point representing a decision made by the player. In a maze game, each branch point is neatly depicted by an intersection in the maze, and the options available to the player are visually presented as the paths available at the intersection. Thus, a maze game presents a clear visual representation of the branching structure of the game. Even more fascinating is the looping structure possible with maze games. A player can return to an intersection in the maze many times. Yet, each time he does so, the options he has take different meanings because the other maze-inhabitants have moved in the interim to a different pattern of positions. In this way, a small number of displayed intersections can represent a huge

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number of branch-points in the game-tree. The analogy with a computer program, in which a small number of program instructions, through looping and branching, can address a large number of specific cases, is striking.

Sports Games
These games model popular sports games. They are anachronisms derived from the early days of computer game design when computer games had no identity of their own. People without original ideas for games fell back on the sports games as models around which to design. This also served a useful marketing purpose: why would a conservative consumer buy a game with a title and subject completely alien to his experience? Better to offer him a game he is already familiar with. Thus we have games based on basketball, football, baseball, soccer, tennis, boxing, and others. All of these games take liberties with their subject matter to achieve playability. The most enjoyable aspects of the computer game have very little to do with the real game. This is fortunate, for a slavish attempt at replication would have produced a poor computer game. Only by substantially altering the original games were the authors able to produce a decent design. Even so, sports games remain the wallflowers of computer gaming. I suspect that sports games will not attract a great deal of design attention in the future. Now that computer games have an accepted identity of their own, the need for recognizable game titles has diminished.

Paddle Games
I use the title "Paddle Games" to cover the PONG-based games. PONG is certainly one of the most successful and fertile of game designs, for it has many grandchildren and great-grandchildren. The central element of the game, that of intercepting a projectile with a paddle-controlled piece, has been used in endless variations. The original PONG pitted two players in an electronic version of ping-pong, hence the name. BREAKOUT was a solitaire version that required the player to chip away at a wall with the ball. The player received points for each brick destroyed. SUPERBREAKOUT introduced variations on this theme with moving walls, extra balls, and other tricks. CIRCUS ATARI introduced parabolic trajectories for the projectiles and a complex moving wall of balloons. WARLORDS; took the genre even further; up to four players (one in each corner) defend brick castles against a projectile bounced around the field by their shield-paddles. In the above games, the player uses the ball as a weapon to batter; in other paddle games the player must only catch the ball, or many balls, rather than deflect it. AVALANCHE is one such game. In this game, the player is at the bottom of the screen and large numbers of rocks are failing; each one must be caught with the player’s piece. The game becomes quite frantic as more and more rocks fall at a faster and faster pace. Another game, CHICKEN, (trademark of Synapse Software) expands on this theme by replacing the rocks with eggs and making each one hatch on striking the ground, forcing the player-hen to jump over it as she moves about.

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The paddle game-system is a very simple one; although I doubt that it has much development potential remaining, I am hesitant to pronounce such a durable old system dead.

Race Games
Some computer games involve a straightforward race. Most of these games allow the player to move at constant speed, but extract time penalties for failure to skillfully negotiate an assortment of hazards. Thus, a player in the APX skiing game DOWNHILL must avoid the trees and rocks; the player’s score is based on his time to complete the course. MATCH RACER by Gebelli Software is a car-racing game with oil slicks and obstacles. NIGHT DRIVER is a car-racing game featuring a first-person view of the road. One problem with all of these games is that they are not true games but puzzles, for there is no real interaction in a race between a player and his opponent. Indeed, it is difficult to identify the opponent in these games. A more involved variation on the race game is DOG DAZE by Grey Chang. This is a true game, not a puzzle. It presents a two-player competitive race game with variable goals and asymmetric obstacles. Each player has a dog; hydrants pop onto the screen at random locations; the players must race to be the first to touch the hydrant, thereby claiming it as their own. Players may not touch hydrants owned by their opponents on pain of being temporarily paralyzed. The game has many interesting twists and turns without being overly complex; it demonstrates that the race game can be a flexible vehicle of game design.

Miscellaneous Games
My taxonomy is flawed; there exist a number of games that do not fit into this taxonomy very well. The first I will mention is DONKEY KONG, (trademark of Nintendo) a game that looks vaguely like a race game with intelligent obstacles. FROGGER (trademark of ________) is another game that defies classification in this taxonomy. It could perhaps be called a maze game with moving walls or obstacles, but the fit is poor. APPLE PANIC by Broderbund Software also defies my taxonomy. In some ways it is like a maze game and in some ways it is a combat game. The pace of the game is oddly slow. I don’t know what to call this game. The fact that these games do not fit my taxonomy does not bother me overly much; I certainly don’t want to create ad hoc categories for individual games. I am content to wait and see other developments before I create new categories or revise old ones.

Strategy games comprise the second broad class of computer games. These games emphasize cogitation rather than manipulation. I do not mean to imply that S&A games are devoid of strategic content; some S&A games do indeed have a strategic element. The major distinguishing factor between strategy games and S&A games is the emphasis on motor skills. All skill-and-action games require some motor skills; strategy games do not. Indeed, real-time play is rare in strategy

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games (this is changing; LEGIONNAIRE from Avalon-HIII is a notable real-time strategy game). Strategy games typically require more time to play than S&A games. Strategy games are nonexistent in the arcades; they are rare on the ATARI 2600; they are almost exclusively restricted to personal computers. I divide strategy games into six categories: Adventures, D&D games, wargames, games of chance, educational games, and interpersonal games

These games derive from one of the oldest computer games, called "Adventure". In these games the adventurer must move through a complex world, accumulating tools and booty adequate for overcoming each obstacle, until finally the adventurer reaches the treasure or goal. Scott Adams created the first set of Adventures widely available for personal computers; his software house (Adventure International) is built on those games. The Scott Adams games are pure text adventures that run in a small amount of memory, so they do not need disk drives; they are also readily transportable to different machines. A short time later Ken and Roberta Williams built On-Line Systems with THE WIZARD AND THE PRINCESS (trademark of On-Line Systems), an adventure that presented pictures of the scenes in which the adventurer found himself. The game itself was not particularly new; the innovation was primarily the use of graphics. Both firms have expanded their lines with more games using the systems they pioneered. Most of these derivative games are structurally similar to the originals, differing in detail, polish, and size. The next variation on the adventure theme was the giant adventure, of which there are several. TIME ZONE by On-Line Systems is one of these. These giant adventures use multiple diskettes to link together a gigantic adventure. As the player solves the puzzle in one environment he moves on to another environment on another disk. The games are structurally identical to earlier games; the only difference is one of magnitude. They take many weeks of play to solve. A new variation on the adventure game genre is DEADLINE (trademark of Infocom), a detective adventure with a number of interesting twists. Its heritage as an adventure is evident in its lack of graphics and its use of an excellent sentence parser. This adventure puts the player in the role of a detective attempting to solve a murder. The game is played in a real-time mode that adds to the interest and challenge of the game. The player searches not for treasure but for information with which to solve the murder. This game shows the potential of the adventure system in that the same system can be used, with the storyline and goals altered, to appeal to a different audience. One of the most clever adventures ever done is Warren Robinett’s ADVENTURE on the ATARI 2600. This adventure follows the same basic format as all adventures, except that it uses absolutely no text. Instead, the user moves through a series of rooms presented in rather simple graphics. Although the graphics and input schemes are radically different, the basic feel of the adventure system has been successfully retained. SUPERMAN, HAUNTED HOUSE, and GALAHAD AND THE HOLY GRAIL by Doug Crockford are all derivatives of this game.

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Adventures are closer to puzzles than to games. As discussed in Chapter One, puzzles are distinguished from games by the static nature of the obstacles they present to the player. Adventures present intricate obstacles that, once cracked, no longer provide challenge to the player. It is true that some adventures push closer to being games by incorporating obstacles such as hungry dragons that in some way react to the player. Nevertheless, they remain primarily puzzles.

D&D Games
A completely independent thread of development comes from the D&D style games. Fantasy roleplaying was created by Gary Gygax with Dungeons and Dragons (trademark of TSR Hobbles), a complex noncomputer game of exploration, cooperation, and conflict set in a fairytale world of castles, dragons, sorcerers, and dwarves. in D&D, a group of players under the guidance of a "dungeonmaster" sets out to gather treasure. The game is played with a minimum of hardware; players gather around a table and use little more than a pad of paper. The dungeonmaster applies the rules of the game structure and referees the game. The dungeonmaster has authority to adjudicate all events; this allows very complex systems to be created without the frustrations of complex rules. The atmosphere is quite loose and informal. For these reasons, D&D has become a popular game, with endless variations and derivatives. D&D first appeared in the mid-70’s; it didn’t take long for people to realize that it had two serious limitations. First, the game needed a group of players and a dungeonmaster, so it was impossible to play the game solitaire. Second, the game could sometimes become tedious when it required lengthy computations and throwing of dice. Many people recognized that these problems could be solved with a microcomputer. The first company to make a D&D style computer game available was Automated Simulations. Their TEMPLE OF APSHAI program has been very successful. They also market a number of other D&D-style games. So far, however, few games have been marketed that truly capture the spirit of D&D. There are several reasons for this. First, most D&D-players are young and don’t have the money for such packages. Second, the adventure games have slowly absorbed many of the ideas of the D&D games. There was a time when we could easily distinguish an adventure from a D&D game with several factors.Adventures were pure text games, while D&D games used some graphics. Adventures were puzzles; D&D games were true games. Adventures were by and large nonviolent, while D&D games tended to be quite violent. Lately, we have seen adventures taking on many of the traits of D&D games, so that it is now harder to tell the difference between them. An ideal example of this phenomenon is ALI BABA AND THE FORTY THIEVES (trademark of Quality Software), a game with the basic elements of both adventures and D&D games. The player must search through a large maze to find and rescue a princess, but on the way he must fight monsters and thieves. The player, as Ali Baba, possesses personal characteristics (dexterity, speed, etc.) that are reminiscent of a D&D game, but he must explore the maze as in an adventure. For these reasons, I feel that this game cannot be classified as either an adventure or a D&D game, but

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rather is a solid example of the merging of these two genres into a new class of games, the fantasy role-playing ("FRP") games. This suggests that we will see more such games combining the "search and discover" aspects of adventure games with the "defeat opponents" aspects of D&D games.

A third class of strategy games is provided by the wargames. Noncomputer wargames as a gaming form have a long heritage. Commercial wargaming goes all the way back to the 1880’s with an American wargame design using wooden blocks. The British have long had a dedicated group of wargamers using miniature models of soldiers and very complex rules. Their games, called miniatures games, have grown in popularity and are now played in the USA. But the largest segment of wargamers in recent years has been the boardgamers. This hobby was founded in the late 1950’s by Charles Roberts, who founded the Avalon-Hill Game Company and created such classic games of the 60’s as BLITZKRIEG, WATERLOO, and AFRIKA KORPS (all trademarks of the Avalon-Hill Game Company). During the 1970’s a new company, Simulations Publications, Inc., turned board wargaming into the largest segment of wargaming. Wargames are easily the most complex and demanding of all games available to the public. Their rules books read like contracts for corporate mergers and their playing times often exceed three hours. Wargames have therefore proven to be very difficult to implement on the computer; we have, nevertheless, seen entries. The computer wargames available now fall into two distinct groups. The first group is composed of direct conversions of conventional boardgames. COMPUTER BISMARK, COMPUTER AMBUSH, and COMPUTER NAPOLEONICS (trademarks of Strategic Simulations, Inc.) are examples of this group of games. These games illustrate the folly of direct conversion of games of one form to another. They parrot successful and respected boardgames, but are themselves not as successful. Because they attempt to replicate boardgames, they are, like boardgames, slow and clumsy to play. The second group of computer wargames are less slavish in their copying of board wargames. My own EASTERN FRONT 1941 is generally considered to be the best of this lot, primarily because of its graphics and human engineering features. Many of the games in this category are experimental; hence the successes are outnumbered by the failures. Avalon-Hill’s first entries into the computer wargaming arena were such experiments. My own TANKTICS game is an early experiment that once was the most advanced commercially available wargame (it was the ONLY commercially available wargame when I first released it in 1978). It is now generally regarded as a mediocre game. It can safely be said that computer wargaming is not a well-developed area of computer gaming. For the moment, computer wargaming is too closely associated with board wargaming in the minds of the public and most designers; until it can shake free from the constraints of boardgames and, establish its own identity, computer wargaming will evolve slowly.

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Games of Chance
Games of chance have been played for thousands of years; their implementation onto computers is therefore quite expectable. They are quite easy to program, so we have seen many versions of craps, blackjack, and other such games. Despite their wide availability, these games have not proven very popular, most likely because they do not take advantage of the computer’s strong points. Furthermore, they lose the advantages of their original technologies. These games demonstrate the folly of mindlessly transporting games from one medium to another.Top

Educational and Children’s Games
The fifth category of strategy games is that of the educational games. Although all games are in some way educational, the games in this set are designed with explicit educational goals in mind. This group is not heavily populated as yet, perhaps because the people interested in educational uses of computers have not yet concentrated much attention on game design. The Thorne-EMI puzzles are good entries in this field, and APX sells a collection of very simple children’s games that have some educational value. Several of the classic computer games are educational: HANGMAN, HAMMURABI, and LUNAR LANDER are the three most noteworthy of these early educational games. SCRAM (a nuclear power plant simulation) and ENERGY CZAR (an energy economics simulation) are two of the more complex programs in the educational games field. My favorite entry to date is ROCKY’S BOOTS (trademark of The Learning Company), a children’s game about Boolean logic and digital circuits. The child assembles logic gates to create simulated logical machines. This game demonstrates the vast educational potential of computer games. Educators are becoming more aware of the motivational power of computer games; with time we can expect to see more entries of the caliber of ROCKY’S BOOTS.

Interpersonal Games
I have been exploring a class of games that focus on the relationships between individuals or groups. One such game explores gossip groups. The player exchanges gossip with up to seven other computer-controlled players. The topic of conversation is always feelings, positive or negative, expressed by one person for another. Adroit posturing increases popularity. Similar games could address corporate politics, soap-opera situations, gothic romances, international diplomacy, and espionage. Although the category is undeveloped, I believe it is important because it addresses fantasies that are very important to people. Many other art forms devote a great deal of attention to interpersonal relationships. It is only a matter of time before computer games follow a similar course.

This concludes the description of my proposed taxonomy. Obviously, this taxonomy has many flaws. This is primarily because the basis of division is not any grand principle but is instead

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historical happenstance. There is no fundamental reason why wargames should be treated any differently than D&D games. Yet, both game systems evolved separately and are historically quite distinct. Similarly, the creation of an educational games category is my response to the efforts of educators to create educational games. With the passage of time, market forces will assert themselves, and a more organized and consistent taxonomy will become possible. People have tried to create educational games, so we now have them. My taxonomy is a patchwork because the set of available computer games is a patchwork. This taxonomy suggests a number of observations about the state of game design with computers. For example, it should be obvious that there are very few basic scenarios for skill-and-action games, each scenario taking one category. The archetypical game in each category spawned a whole family of imitators, variations, and improvements. Moreover, the archetypical game in each category was seldom the big moneymaker; instead, the archetypical game was followed by several successor games that improved on it until one game hit the nail on the head. Thus we have COMBAT leading to SPACE INVADERS in the combat category, DODGE 'EM leading to PAC-MAN in the maze category, and PONG leading to SUPERBREAKOUT in the paddle category. Another lesson that arises from this taxonomy is that the Analogy games are still in a very poorly-developed state in comparison to the S&A games. While S&A games have fairly clear-cut categories that make sense, the categories in strategy games are less satisfying and the distinctions between categories are muddier. This ambiguity suggests that much creative opportunity remains in the strategy games field. A taxonomy reflects the body of material it attempts to organize. The state of computer game design is changing quickly. We would therefore expect the taxonomy presented here to become obsolete or inadequate in a short time. New taxonomies must be created to reflect the changes in the marketplace in the next few years. For the present, however, the proposed taxonomy can provide us with an organized way to view the menagerie of games while suggesting new areas to explore.

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CHAPTER FOUR The Computer as Game Technology



very art form is expressed through a physical medium. The control and manipulation of this physical medium is a technical problem that the artist must master before she can express herself through it. Thus, the sculptor must thoroughly understand the limitations

of marble, brass, or whatever medium she uses. The painter must fully understand the technology of paint and the behavior of light. The musician must be deeply skilled in the technology of sound creation. So too must the computer game designer thoroughly understand the medium with which she works. The computer offers special possibilities and imposes special constraints on the designer. In this chapter I will discuss the nature of these possibilities and constraints. A few examples of a game technology operating at a simpler level may help establish basic princi-

Cards are one such simpler game technology. We have here a very simple set of physical equipment---52 pieces of cardboard, imprinted on one side with a uniform pattern, and on the other side with distinct symbols. The key traits of this equipment can be summarized as follows: 1) There are many cards. 2) Each card is unique. 3) Each card possesses a numeric value. 4) Each card possesses a suit, a two-bit value. 5) The identity of a card can be selectively revealed. 6) Each card is easily assignable to an owner. These six characteristics are the fundamental properties of the card, technology that constrain the design of all card games. Each characteristic carries implications for game design with cards. Some things are easy to do with this technology and some things are hard to do with it. For example, games of probability are easily implemented with this technology, for the two characteristics (numeric value and suit) can be combined into many, many sets according to laws of probability. The limitations on information created by the cards can be used to create games of guesswork and intuition. Indeed, one of the most intriguing of card games, poker, is based not so much on cold probability assessments as on the deceptions made possible by the limited information employed in the game. Like every other technology, cards also have their weaknesses. For example, it would be very tricky to design a card game for more than 52 players, because there are only 52 cards in one deck. It would also be very difficult to design a good skill-and-action game using cards as a technology. Another tough design challenge would be a good athletic game using cards. Games meeting these conditions could be implemented with cards, but they probably would not be very good games.

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This doesn’t mean that cards are a bad game technology. Some things can be done well with cards, and other things can’t. Another game technology, that of the boardgame, is somewhat more flexible than cards. This technology is so much more flexible than cards that I cannot devise a list of defining characteristics as I could with cards. Boardgames can be described but not rigorously defined. They use a large surface of paper or cardboard on which are printed various images, normally taking the form of a stylized map. Frequently the area represented on the map is divided into discrete regions by either a regular geometric pattern (rectgrid or hexgrid), a segmented path to be traversed, an irregular division of regions, or a network of points connected by paths. The map itself remains the same throughout the game; players designate changes in the situation with a set of markers that can be moved about on the map. Sometimes a randomizing machine is used to determine outcomes of random processes; a spinner or dice are most frequently used for this purpose. Sometimes cards from a special set are drawn to provide this randomizing function. This technology has proven to be very successful for game designers. It easily accommodates groups of players, and with appropriate game design can address a very wide range of gaming situations. Chess is certainly the all-time classic boardgame. MONOPOLY (trademark of Parker Brothers), a successful early boardgame, concerns real estate transactions. Other boardgames have addressed such topics as life goals, solving a murder, and race relations. The most ambitious modern boardgames are the wargames. Among these are games with boards of some 25 square feet, several thousand movable pieces, and a rules manual 50 pages long. A small industry has sprung up around these designs, complete with historical research, star designers, and its own jargon. Boardgames provide a flexible and powerful technology for game designers. In recent years, however, we have seen a stagnation in designs with the board technology. Many new boardgames look like cheap copies of MONOPOLY. Wargames, after showing a burst of creative energy in the 60’s and 70’s, have started to stagnate. Few fundamentally new ideas are being introduced in this arena. It may be that we have mined this vein to the limits of its productive capacity. What are the limitations of this technology? First and foremost, it is very difficult to maintain privileged information in a boardgame. All players can see the board and the position of all the markers. Second, the mechanics of handling all the pieces must be managed by the players. In some cases this can become a sizable chore, as in the aforementioned monster wargame. For this reason most boardgames are long affairs, frequently filling an evening. Short boardgames playable in twenty minutes or less are quite rare. Finally, should the pieces be disturbed, a boardgame is easily ruined. The central point of the preceding discussion is that every game utilizes some technology, and that each technology has strengths and weaknesses, things that it can do well and things that it can do poorly. The astute game designer must fully grasp the strengths and weaknesses of the technology s/he uses. Let us now examine the computer as a game technology.

The Art of Computer Game Design


The most striking feature of the computer in a game context is its responsiveness. Responsiveness is vital to the interactiveness that is so important to any game. The computer can respond to the human player’s wishes in a huge variety of ways. If the action in a card game or board game starts to drag, the players have no choice but to plod through it or take desperate measures. There is no reason why a computer game in similar straits could not speed up the game on demand. It could change the length of the game, or the degree of difficulty, or the rules themselves. SPACE INVADERS (trademark of Taito America) for the ATARI 2600 provides an example of such performance. The player can select one or two-player versions, visible or invisible invaders, stationary or moving shields, fast or slow bombs, and a variety of other options. In effect, the player chooses the rules under which he plays. The game is responsive to his wishes. This responsiveness arises from the computer’s plasticity. The computer is dynamic; it imposes little constancy on any element of the game. Boardgames, cardgames, and athletic games all have invariables that constrain the designer. Once you have printed up 100,000 game boards it becomes very difficult to modify the map. Try as we may, we can’t have 53-card stud; the card decks aren’t made that way. And should some miracle of science produce more elastic footballs that kick further, we will not be able to simply extend football stadiums without spending many millions of dollars. The computer is far less restrictive. All of the game parameters are readily changed, even during the course of the game. There is nothing stopping us from creating a football game in which the goal post recedes from the visiting team. Territories in wargames can be switched around the map of the globe more easily than we move a chair in the living room. This flexibility is of paramount importance tothe game designer. As yet, it has been put to little use. A second feature of great value is the computer’s ability to Motion as game referee. All other game technologies demand that somebody take the time to handle the administrative responsibilities of the game. Athletic games are most demanding; they require several impartial referees or umpires to administer the rules of the game and adjudicate disputes. Card games and boardgames require that the players also function as referees. This is seldom a problem with card games, but it can be a big load with boardgames, especially the more complex ones such as the wargames. Rules disputes and administrative foul-ups are part of the unavoidable dangers of boardgames. The computer can eliminate all of these problems. It can administer the game, freeing the player to concentrate on playing it. This allows one other big advantage: the computer can implement complex arithmetic and logical rules. With other technologies, game rules must be overly simple because the humans implementing them cannot be trusted to perform simple numerical computations. The computer eliminates this restriction. For example, in the original version of EASTERN FRONT 1941, I was able to use exceptionally complex victory calculations. Most board-level wargames about the eastern front in World War II assign victory points for captured cities, and perhaps for casualties inflicted and sustained. A more complex calculation recognizing the realities of the campaign would be too tedious for human computation. Original EASTERN FRONT 1941 was able to calculate not only cities captured and

The Art of Computer Game Design


casualties inflicted and sustained, but also the eastward progress of every German unit as well as the westward resistance of every Russian unit. The game is thereby able to provide a more realistic and meaningful measure of the player’s performance. The third advantage of the computer is in real-time play. Other game technologies must have pauses and procedural delays while administrative matters are dealt with. The computer is so fast that it can handle the administrative matters faster than the humans can play the game. This makes real-time games possible. Skill-and-action games are the direct result. The speed of the computer also eliminates the need for turn-sequencing so common in card games and boardgames. The fourth strength of computers for game design purposes is their ability to provide an intelligent opponent. All other games require a human opponent (exception: solitaire card games, but they are actually puzzles rather than games). The greatest success so far has been with chess-playing games. Programs written for microcomputers can now play a chess game well enough to challenge most non-rated players. These games represent the best we have achieved to date in game artificial intelligence. Most games are far less intelligent. Instead, they rely on overwhelming numerical advantage to make up for the superior intelligence of the human player. With the passage of time, we can expect to see more intelligent algorithms that provide more challenging play from the computer. The fifth strength of the computer is its ability to limit the information given to the players in a purposeful way. This capability can be of great value. Limited information forces the player to use guesswork. The nature of this guesswork can be very intriguing. For example, guessing a random number between one and ten is not a very interesting challenge, but guessing your opponent’s resources based on your assessment of his actions and personality is a far more interesting exercise. When the guesswork is included in the framework of a complex and only partially known system, the challenge facing the human player takes on a decidedly real-life texture. Limited information provides another important bonus. Games are an unreal representation of a real-world problem. The player must use his imagination to make the unreal situation seem real. Limited information encourages the use of imagination. If we know all the pertinent facts, we can treat the problem as a simple problem of deduction. But if we know only a portion of the truth, our minds grope for an appropriate model on which to hang our projections. What model could be more appropriate than the reality that the game attempts to re-create? We are therefore forced by lack of information to imagine ourselves in the real-world predicament postulated by the game so that tie may deal with the problems imposed by the game. In the process, the illusion of reality is heightened. The game draws us into its fantasy world more effectively. The sixth feature offered by computers is their ability to utilize data transfer over telephone lines for game play. The use of telecommunications for game play makes possible game structures that are out of the reach of other technologies. It allows us to create games with huge numbers of players. Until now, administrative problems have made it necessary to limit the number of players in

The Art of Computer Game Design


any game. Six players is a rough upper limit for a non-refereed game; twelve players will require several referees and twenty players or more will require many referees. Obviously, games with hundreds of players will face many administrative problems. Indeed, the logistic problems of assembling all th players are themselves prohibitive. All these problems are solved by computers linked through a telecommunications network. With this technology it should be possible to design games knitting together thousands of players scattered all over the continent. Players could drift into and out of the game at their whim; with large numbers of players the coming and going of individuals will not be detrimental to the game. Like any technology, computers have weaknesses as well as strengths. The first and most painful weakness is the limited I/O capability of most computers. The computer itself may be supremely responsive, but if the human player can’t tell it what he wants, or fails to understand the computer’s response, the computer’s effective responsiveness is nil. In other words, the computer must communicate its responsiveness to the human; it does so through I/O. Most output is through graphics and sound; most input is through keyboard, joystick, and paddle. Graphics are the first component of output. Good graphics are hard to come by. Even the Atari Home Computer System, boasting the best graphics in the microcomputer world, has graphics limitations that severely constrain the game designer. You simply cannot show all the graphic details that you would like to show. For example, I suspect that few boardgame boards could be duplicated on a single screen by this machine. The number of colors, the mixing of text with highresolution graphics, and the size of the board all combine to make the task hopeless. It is possible to use a variety of tricks to produce something that is functionally similar to any given game board. We could reduce the number of colors displayed, we could dispense with text, and we could design an oversize display through which the user must scroll. EASTERN FRONT 1941 uses all of these tricks, and the result is quite usable, but the game wends a tortuous path past the graphics constraints of the computer. Of course, the computer also boasts some graphics advantages. I have yet to see the boardgame that could show animation or change itself around the way a computer game could. These sensory features can dramatically increase the impact of any game. So the graphics picture is not all bad. Another I/O restriction comes from the input requirements. Input to the computer must come in through the keyboard or the controllers. This can make things very difficult for the game designer. In the first place, you can’t say much with a joystick or keyboard. A joystick can say only five fundamental words: "up", "down", "right", "left", and "button". A keyboard can say more, but only through a lengthy and error-prone sequence of key presses. The human who wishes to express a meaningful communication to the computer must successfully enter a long and clumsy string of simple commands. Input is made even more difficult by the indirectness of keyboards and joysticks. There is very little about such devices that directly corresponds to real-world activities. Actions that are simple and obvious with other technologies become arcane with the computer. If I give you a bat and tell you that your goal in baseball is to hit the ball, you will have few

The Art of Computer Game Design


problems deciding that you should swing the bat at the ball. A computer baseball game is not so easy to figure out. Do you press H for "hit" or S for "swing" or B for "bat"? Do you press the START key or press the joystick trigger? Perhaps you should swing the joystick by its cable at the ball displayed on the television screen. After I/O, the second weakness of the personal computer is its single-user orientation. These machines were designed for one person to use while a seated at a desk. If two people are to use it, they may be forced to exchange seats, a clumsy and distracting procedure. With joysticks or paddle controllers the problem is diminished but not eliminated. This is one reason why so many computer games are solitaire and has led to the accusation that computer games are anti-social. A boardgame invites a group of people to sit around the table. A computer game encourages one player, accepts two, and discourages more. The final weakness of the computer to be considered here is the requirement that it’s programmed. No other game technology imposes so harsh a demand on the game designer. The boardgame designer can sketch an adequate board and construct some simple playing pieces that will serve quite effectively. When the time comes to produce the game, the designer’s amateur efforts can be handed to a professional who can produce a quality version of the prototypes made by the designer. For this reason the designer need not concern himself with the technical aspects of game production. The computer game designer does not have life so easy. The design must be implemented on the computer by programming it. Programming itself is a tedious and difficult process, and it is not easily delegated, for the programming effort exerts a major influence over the design process. Implementing a design well is a major hurdle for any computer game designer.

How do we translate an understanding of these strengths and weaknesses of the computer into a set of guidelines for game designers? The characteristics described above imply a variety of precepts.

(Introducing our idiot cartoon hero. A rocket lies on its side. A wheel-less baby carriage lies nearby. Our hero is walking from the baby carriage toward the rocket, carrying some baby carriage wheels and a hammer.) The first-precept can be summarized with the aphorism: "Work with the grain of the machine, not against it." Too many game designers set out with unrealistic goals. They attempt to force the machine to perform tasks for which it is not well-suited. In saying this, I do not excuse lazy programming. We must remember that the computer is the servant of the human; the convenience

The Art of Computer Game Design


of the computer is not of interest to the designer. Our goal is to extract maximum performance from the computer, to make it work its best. We can only do this by making it perform functions which it performs well. Case In Point: Hexgrids An example of this principle might be illuminating. Board wargames are traditionally executed on maps that use a hexgrid system. This regularizes movement and defines positions. Hexgrids are preferred over rectgrids for several reasons. First, rectgrids have diagonals; two units can be diagonally adjacent. This situation can be very messy; rules to cope with it are always burdensome and confusing. Hexgrids have no diagonals, so they eliminate the problem. Second, hexgrids allow a player a choice of six directions in which to move, while rectgrids offer only four directions. The greater range of choice allows the player to control more finely the movements and positioning of his pieces. It therefore seems natural that designers of computer wargames would also use hexgrids for their maps. Indeed, most computer wargames do so ---but it is a terrible mistake. The hex does have advantages, but it imposes a penalty on computer wargames that does not apply to boardgames. You can print anything you desire on a piece of paper, but the graphic display of the computer is not so accommodating. The display system of the television set is fundamentally rectangular in its architecture. Horizontal lines are stacked in a vertical sequence. Such a display can very easily handle rectangular shapes; hexagonal shapes just don’t work very well. To draw a hex the program must draw four diagonal lines, each one composed of a set of staggered dots. To make the hexgrid recognizable the lines must be surrounded by an exclusion zone at least one pixel wide; this consumes a large portion of the screen area if the hexes are small and dense. If they are larger, less screen area is consumed by the gridwork but fewer hexes can be shown on a single screen. Moreover, joysticks cannot be easily used with hexgrids because joysticks are set up with rectangular geometry. I do not wish to imply that hexgrids cannot be implemented on personal computer displays; on the contrary, they have already been implemented on many personal computers. The problem is that they are clumsy to display, lacking in graphic detail, and difficult to use. They just don’t work smoothly. A topologically identical solution has been used in a few games: horizontally staggered rows of squares ("bricks") are used in place of hexes. This system retains the flexibility of hexes while imposing fewer display problems; it remains very difficult to use with a joystick. For these reasons I went back to rectgrid for EASTERN FRONT 1941. My decision was not based on laziness or unwillingness to tackle the problem of hexgrids; indeed, I had already solved the problem with another game (TACTICS) and could easily have transported the code. The experience I gained in working with the earlier code convinced me that hexgrids weren’t so important. The success of EASTERN FRONT 1941 seems to indicate that the lack of hexgrids need not impose a handicap.

The Art of Computer Game Design


(Now our hero is plummeting earthward from the top of a cliff, furiously flapping makeshift wings attached to his arms.) One of the most disgusting denizens of computer gamedom is the transplanted game. This is a game design originally developed on another medium that some misguided soul has seen fit to reincarnate on a computer. The high incidence of this practice does not excuse its fundamental folly. The most generous reaction I can muster is the observation that we are in the early stages of computer game design; we have no sure guidelines and must rely on existing technologies to guide us. Some day we will look back on these early transplanted games with the same derision with which we look on early aircraft designs based on flapping wings. Why do I so vehemently denounce transplanted games? Because they are design bastards, the illegitimate children of two technologies that have nothing in common. Consider the worst example I have discovered so far, a computer craps game. The computer displays and rolls two dice for the player in a standard game of craps. The computer plays the game perfectly well, but that is not the point. The point is, why bother implementing on the computer a game that works perfectly well on another technology? A pair of dice can be had for less than a dollar. Indeed, a strong case can be made that the computer version is less successful than the original. Apparently one of the appeals of the game of craps is the right of the player to shake the dice himself. Many players share the belief that proper grip on the dice, or speaking to them, or perhaps kissing them will improve their luck. Thus, the player can maintain the illusion of control, of participation rather than observation. The computer provides none of this; the mathematics may be the same, but the fantasy and illusion aren’t there. In one way or another, every transplanted game loses something in the translation. It may also gain something, but it always loses something. This is because any game that succeeds in one technology does so because it is optimized to that technology; it takes maximum advantage of the strengths and avoids the weaknesses. The transplanted version uses the same design on a different set of strengths and weaknesses; it will almost certainly be a lesser product. Any memorable artistic expression is as much a creature of its vehicle of expression as it is an image of a thought. Shakespeare reads best in Elizabethan English; translation to modern English loses some of the verve and linguistic panache that we find so entertaining. The rhetoric of Isocrates, dull and drab in English, acquires a compelling cadence in Greek that thrills the listener. Great books that touched our souls when we read them almost always disappoint us when we see their movie adaptations. Why should computer games be immune to this law of loss on translation?

(Now our man is putting the final touches onto a gigantic and complex machine with pipes, valves, smokestacks, and many wires. On the front face of the machine is a sign that reads,

The Art of Computer Game Design


"Make your move". Underneath it are two buttons labeled "CHOICE A" and "CHOICE B". To the right of this are a pair of illuminable signs, one reading, "YOU WIN!!!", the other reading "YOU LOSE!!!" ) As I mentioned earlier, the computer’s ability to calculate is a strength, but it’s I/O is a weakness. Thus, the primary limitation facing the computer game designer is not in the machine’s ability to perform complex computations, but in the I/O: moving the information between the computer and the human player. The game must be designed in such a way that the information given to the player flows naturally and directly from the screen layout and sound output. I have seen far too many games with good game structures that were ruined by poor I/O structures. The user was never able to appreciate the architectural beauties of the game because they were buried in a confusing display structure. Even worse are the games that sport poor input arrangements, especially poor use of the keyboard. Most game players find keyboards difficult to use smoothly. Difficulty can in some cases create challenge, but difficulties with keyboards generate only frustration. The implementation of the game will be dominated by the limitations of I/O. What can and cannot be displayed, what can and cannot be inputted, these things must decide the shape of the same. A comparison of two of my own games provides an excellent example of the importance of I/O structures. EASTERN FRONT 1941 and TANKTICS (trademark of Avalon-Hill) are both wargames dealing with World War II. Both provide reasonably intelligent opponents, complex detailed simulation, a rich variety of options, and thought-provoking strategic challenges. In all these respects, they are roughly equivalent. They differ primarily in their I/O. EASTERN FRONT 1941 was designed around its I/O; it provides clean, informative graphics and an intuitively obvious joystick input system. By contrast, TANKTICS was designed around its game structure; its keyboard input system is clumsy and confusing and its alphanumeric; screen display is cryptic. EASTERN FRONT 1941 has been acclaimed by the critics and has received awards; TANKTICS has been panned. The quality of a game’s I/O structure is crucial to its success.

(Our hero at the controls of his custom motorcycle, 20 feet long, equipped with numerous rearview mirrors, power steering, brakes, and throttle, adjustable seats, adjustable handlebars, windshield wipers on several windshields and on each mirror, television, hamburger dispenser, etc. The artist can use imagination here.) Many game designers fail to keep the overall structure of their game close to heart as they develop the details of the game structure. As they encounter design problems, they resort to quick patches that are grafted onto the main game structure without due regard to the impact such grafts have on the overall cleanliness of the design. A game must have artistic unity if it is to have emotional impact on its audience. Artistic unity can only be achieved by sticking close to the theme and eschewing distracting details.

The Art of Computer Game Design


I refer to any factors that do not comport with the central theme of the game as "dirt." The debilitating nature of dirt is seldom recognized, because dirt also endows a game with "color", namely the texture or feel that makes the game seem real. It is true that proper use of this kind of color will indeed enhance a game. However, the game designer must realize that color is obtained at the price of a certain amount of dirt. The critical quantity then becomes the ratio of color to dirt. The designer always desires the highest possible ratio, but sometimes, to increase the absolute amount of color, s/he must accept some more dirt. In all cases, the inclusion of dirt into a game must be a conscious trade-off on the part of the game designer, not an accident springing from the desire to quickly resolve some irritating problem. Dirt most often arises from special-case rules that are applied rarely. For example, EASTERN FRONT 1941 has a number of special-case rules that add dirt to the game. The worst is the rule forbidding Finnish units to attack. Inasmuch as there are only two Finnish units, this rule has very little significance to the game as a whole, yet the player must still be aware of it. It clutters up the game and the player’s mind without adding much. (I had to put it in to solve a design problem: what’s to stop the Finns from taking Leningrad all by themselves?) A less dirty rule provides that Axis allies (Rumanian, Hungarian, and Italian units) fight with less determination than the Germans. There are six of these units in EASTERN FRONT 1941; thus, the rule is not quite so special a case and hence not quite so dirty. There is a rule in EASTERN FRONT 1941 that armored units move faster than infantry units. EASTERN FRONT 1941 has many armored units; thus, this rule is not a particularly special case, because it applies to a goodly portion of all units. It is therefore not dirty. I can generalize these observations by saying that the narrower the range of application of a rule, the dirtier it is. My precept against dirt thus requires the designer to formulate a set of rules that cover the entire game situation without recourse to special case rules. In the perfect game design, each rule is applied universally. We can never achieve the perfect design, but we can and should strive to give each rule the widest possible application. The player must consider the implications of each rule while making every decision in the game. There is a school of game design that I derisively label the "humongous heap" school of game design. Perpetrators of this philosophy design a game by selecting a simple structure and piling onto it the largest possible jumble of special odds and ends (they call them "features"). These people design with a shovel instead of a chisel. They confuse magnitude with magnificence, intricacy with insight.

(Our idiot is juggling. Beside him another man is juggling five or six numbers comfortably and happily. The idiot is staring upward in stark terror, arms outstretched in a futile attempt to catch an avalanche of numbers that will simply crush him.)

The Art of Computer Game Design


The role of information storage in a computer is often misunderstood. A computer is not primarily an information storage device; it is instead an information processing device. Information storage is a necessary precondition for information processing, but it is not an end in itself. Greater amounts of stored information permit greater amounts of information processing, but if the processing capability is insufficient to realize the full potential of the storage, then that storage is wasted. The ideal program strikes the optimum balance between storage and processing. Most game programs I have seen are long on storage and short on processing. This is because data for storage facts are easier to come by than process-intensive material-program code. In taking the path of least resistance, most game designers end up going downhill. Thus, a game that sports huge quantities of static data is not making best use of the strengths of the machine. A game that emphasizes information processing and treats information dynamically is more in tune with the machine. Relegate all static information to a rules book; paper and ink are still a better technology than personal computers for storing static information. Information that lies around and does little, that must be dusted off before using, has no place inside the microcomputer. As you look over your program listing, you should inspect each byte and ask yourself, "Am I getting my money’s worth from this byte? Is it working hard for me, doing useful things frequently? Or is this a lazy byte that sits idle for hours and is used only rarely?" Fill your program with active bytes that do things, not lazy bytes. Lazy bytes are often associated with dirty rules (they like to hang out together in sleazy pool halls). Dirty rules are special cases that occur rarely. If they occur rarely, the bytes associated with them are not used often, hence they are lazy bytes. Another argument in favor of this precept arises from more fundamental considerations on the nature of game play. Interactiveness is a central element of game enjoyment. As mentioned earlier, the computer’s plasticity makes it an intrinsically interactive device. Yet, the potential inherent in the computer can easily go unrealized if it is programmed poorly. A program emphasizing static data is not very dynamic. It is not plastic, hence not responsive, hence not interactive. A processintensive program, by contrast, is dynamic, plastic, responsive, and interactive. Therefore, store less and process more. One last argument has more to do with games than computers. (You will remember from Chapter One that a game is distinguished from a story by the network of options that a game has, as opposed to the single richly-developed thread of a story. Much of the quality of a story is derived from the richness of the information it contains. A story is thus all information and no processing. A game derives its quality from the richness of the network of options it presents. These options are only accessible through the process-intensive aspects of the game. Games that are information-rich and process-poor are closer to stories than to the ideal game.

The Art of Computer Game Design


(Our hero is now a pole vaulter handcuffed to a high jumper. They are attempting to leap; their attempt is obviously going to collapse in a tangle of limbs. Their facial expressions indicate that they are aware of the likely outcome.) Games must be designed, but computers must be programmed. Both skills are rare and difficult to acquire, and their combination in one person is even more rare. For this reason many people have attempted to form design teams consisting of a nontechnical game designer and a nonartistic programmer. This system would work if either programming or game design were a straightforward process requiring little in the way of judicious trade-offs. The fact of the matter is that both programming and game design are desperately difficult activities demanding many painful choices. Teaming the two experts together is rather like handcuffing a pole vaulter to a high jumper; their resultant disastrous performance is the inevitable result of their conflicting styles. More specifically, the designer/programmer team is bound to fail because the designer will ignorantly make unrealistic demands on the programmer while failing to recognize golden opportunities arising during the programming. For example, when I designed the game ENERGY CZAR (an energy-economics simulation game), I did not include an obviously desirable provision for recording the history of the player’s actions. During the final stages of the game’s development, virtually everyone associated with the project suggested such a feature. From technical experience, I knew that this feature would require an excessive amount of memory. A nontechnical designer would have insisted upon the feature, only to face the disaster of a program too big to fit into its allowed memory size. Another example comes from EASTERN FRONT 1941. While writing the code for the calendar computations, I realized that a simple insertion would allow me to change color register values every month. I took advantage of this opportunity to change the color of the trees every month. The improvement in the game is small, but it cost me only 24 bytes to install, so it proved to be a very cost-effective improvement. A nontechnical game designer would never have noticed the opportunity; neither would a nonartistic programmer. There is no easy way to produce good computer games. You must start with a good game designer, an individual with artistic flair and a feel for people. That person must then learn to program. The opposite direction of development (from programmer to designer) will not work, for programmers are made but artists are born. When eventually you get that rare individual who is both designer and programmer, then you can subordinate designers and programmers underneath her, so as to multiply her creative power. In the process, the subordinates will receive valuable training. In all cases, the creative process must be unified in a single mind. Committees are good for generating red tape, deferring decisions, and shirking responsibility, but they are useless when it comes to creative efforts.

The Art of Computer Game Design


In this chapter I have discussed the computer as a technology for game design. Discussions of computers and their impact on society tend to become polarized between the "gee whiz school and the cynical school. The former group sees a rosy future of countless triumphs wrought by the computer -- "Every day in every way, better and better." The latter group sees computers as a dehumanizing threat, a waste of time, or yet another vehicle for the expression of human perfidy. In this chapter, I have tried to present computers as just another technology, like hammer and nails, clay and stone, paper and ink. Like any technology, they can do some things well. Like any, technology, they do some things poorly. The artist’s role is to deviously evade their weaknesses while capitalizing their strengths to greatest advantage.

The Art of Computer Game Design


CHAPTER FIVE The Game Design Sequence


ame design is primarily an artistic process, but it is also a technical process. The game designer pursues grand artistic goals even as she grinds through mountains of code. During the process of developing the game, she inhabits two very different worlds, the

artistic world and the technical world. How does one manage the integration of such dissimilar worlds? In short, how does one go about the process of designing a computer game? In previous chapters I have touched on some of the questions related to this process; I have also laid down a few precepts. In this chapter I will suggest a procedure by which a computer game could be designed and programmed. The procedure I will describe is based on my own experiences with game design, and reflects many of the practices that I use in designing a game. However, I have never used this procedure in a step-by-step fashion, nor do I recommend that any person follow this procedure exactly. In the first place, game design is far too complex an activity to be reducible to a formal procedure. Furthermore, the game designer’s personality should dictate the working habits she uses. Even more important, the whole concept of formal reliance on procedures is inimical to the creative imperative of game design. Finally, my experience in game design is primarily with personal computers, so my suggestions are not completely applicable to arcade game designers or home video game designers. I therefore present this procedure not as a normative formula but as a set of suggested habits that the prospective game designer might wish to assimilate into her existing work pattern. With these important qualifications in mind, let us proceed.

This vitally important step seems obvious, yet is ignored time and time again by game designers who set out with no clear intent. In my conversations with game designers, I have many times discerned an indifference to the need for clear design goals. Game designers will admit under close examination that they sought to produce a "fun" game, or an "exciting" game, but that is more often than not the extent of their thinking on goals. A game must have a clearly defined goal. This goal must be expressed in terms of the effect that it will have on the player. It is not enough to declare that a game will be enjoyable, fun, exciting, or good; the goal must establish the fantasies that the game will support and the types of emotions it will engender in its audience. Since many games are in some way educational, the goal should in such cases establish what the player will learn. It is entirely appropriate for the game designer to ask how the game will edify its audience. The importance of a goal does not become obvious until later in the game design cycle. The crucial problems in game development with microcomputers are always problems of trade-offs. Everything that the game designer wants to do with her game costs memory, and memory is always in short supply with microcomputers. Thus, the designer must make trade-offs.

The Art of Computer Game Design


Some game features can be included, and some must be rejected. At two o’clock in the morning, when you must face the awful decision of rejecting one of two highly desirable features, the only criterion you will have for making this painful choice will be the goal you have established for the game. If your goals are clear, your decision will be painful but obvious; if your goals are murky, you may well make the wrong choice, and whatever you choose, you will never know if your decision was correct. How do you select a proper goal? There is no objective answer to this question; the selection of a goal is the most undeniably subjective process in the art of computer game design. This is your opportunity to express yourself; choose a goal in which you believe, a goal that expresses your sense of aesthetic, your world view. Honesty is an essential in this enterprise; if you select a goal to satisfy your audience but not your own taste, you will surely produce an anemic game. It matters not what your goal is, so long as it is congruent with your own interests, beliefs, and passions. If you are true to yourself in selecting your goal, your game can be executed with an intensity that others will find compelling, whatever the nature of the game. If you are false to yourself, your game will necessarily be second-hand, me-too. There are situations in which it is not quite possible to attain the purity of this artistic ideal. For example, I would not claim that only immature, childish people should design games for children. Nor would I suggest that good shoot-’em-up games can only be done by shoot-’em-up personalities. The realities of the marketplace demand that such games be written, and it is better that they be written by mature professionals than by simpering fools. Such emotionally indirect games, however, will never have the psychological impact, the artistic power, of games coming straight from the heart. Once you have settled on your goal, you must select a topic. The topic is the means of expressing the goal, the environment in which the game will be played. It is the concrete collection of conditions and events through which the abstract goal will be communicated. For example, the goal of STAR RAIDERS apparently concerns the violent resolution of anger through skillful planning and dexterity. The topic is combat in space. The goal of EASTERN FRONT 1941 concerns the nature of modern war, and especially the difference between firepower and effectiveness. The topic is the war between Russia and Germany. Most game designers start off by selecting their topic, with their goals subordinated to their topic. Indeed, they commonly describe a game under development by its topic rather than its goal. When I tell other designers that I am working on a game about leadership, I am met with quizzical expressions. Is it a space game, or a wargame, or a dungeon game, they wonder; they seem satisfied when I tell them it’s a game about King Arthur. It is a serious mistake to subordinate the goal to the topic. Although your initial flash of inspiration may focus more on the topic than the goal, you must have the determination to take control of the design and impose your own goals onto the topic rather than allowing yourself to be swept away by the momentum of the topic.

The Art of Computer Game Design


Selecting a good topic can be time-consuming, for each potential topic must be carefully examined for its ability to successfully realize the goals of the game. Many topics carry with them some excess emotional baggage that may interfere with the goals of the game. For example, my most recent game design effort uses the Arthurian legends as its topic. My goal in the game is to examine the nature of leadership. I found the Arthurian legends to be a compelling vehicle for this goal. Unfortunately these legends contain a strong component of male braggadocio, the vanquishing of opponents by brute force. This theme directly contradicts some of the points I want to make with the game, thus weakening the utility of this topic for my ends. I find the legends so powerful and so malleable that I am willing to accept and work around this potential pitfall.

With a goal and topic firmly in mind, the next step is to immerse yourself in the topic. Read everything you can on the topic. Study all previous efforts related to either your goal or your topic. What aspects of these earlier efforts appeal to you? What aspects disappoint or anger you? Make sure that you understand the mechanics of the environment your game will attempt to represent. Your game must give the authentic feel, the texture of the real world, and this can only be achieved if you firmly understand the environment of the game. While researching EXCALIBUR, I studied the history of Britain during the period AD 400-700. I found little in the history books that was harmonious with my goal of depicting the nature of leadership. But in the Arthurian legends I found recurring themes more closely related to my goal. You may well find yourself adjusting your goals as you perform this research function; such erratic decision-making is an embarrassing admission of poorly-defined goals, but reflects an honest willingness to adapt to the exigencies of the topic-environment. It is a departure from the ideal in which I have sinfully indulged myself many times. During this phase it is critical that you commit little to paper and above all, WRITE NO CODE! Take long walks as you contemplate your game. Cogitate. Meditate. Let the goal, the topic, and the facts gleaned from your research simmer together in the innards of your mind. Weave them together into a whole. Take your time with this phase; impatience now will lead to mistakes that will kill the game. I give myself at least three weeks to develop a game idea in this stage before proceeding to the next step. With EXCALIBUR I expended several months on this stage. During this time I kept my fidgeting hands busy by writing an opening graphic display that had little relevance to the final game. You will generate during this phase a great variety of specific implementation ideas for your game. They will not all fit together neatly---like any hodgepodge, they will require much sorting and rearranging before they can be used. You should not wed yourself to any of them. A large collection of candidates for implementation is a useful resource during the design phase. A laundry list of implementation ideas that must be included is a liability. Indulge yourself in creating implementation ideas, but be prepared to winnow them ruthlessly during design.

The Art of Computer Game Design


For example, I recently designed a corporate politics game in association with another person. During the research and preparation phase, we came up with a long list of clever ideas that we wanted to into the game. We had agreed that the game would have a feminist point of view without being preachy. We wanted to have a demanding boss, tough projects, deadlines, brownie points, one male chauvinist pig, neutral males, neutral females, family and home obligations, mentors, and the competition for the big promotion. We managed to include almost all of these ideas in the final design. We were not able to integrate the family elements into the game. Every design we created failed to do justice to our desires. In the end, we had to discard this desirable element.

You now have a clear idea of the game’s ideals but you know nothing of its form. You are now ready to begin the concrete design phase. Your primary goal in the design phase is to create the outlines of three interdependent structures: the I/O structure, the game structure, and the program structure. The I/O structure is the system that communicates information between the computer and the player. The game structure is the internal architecture of causal relationships that define the obstacles the player must overcome in the course of the game. The program structure is the organization of mainline code, subroutines, interrupts, and data that make up the entire program. All three structures must be created simultaneously, for they must work in concert. Decisions primarily relating to one structure must be checked for their impacts on the other structures..

I/O Structure
I prefer to start with the I/O structure, for it is the most constraining of the three. I/O is the language of communication between the computer and the player; like any human language, it is the funnel through which we must squeeze the avalanche of thoughts, ideas, and feelings that we seek to share with our fellow human beings. I/O will dictate what can and cannot be done with the gains. I/O is composed of input and output. Unlike human languages, the two are not symmetric. The computer has two means of output to the human: graphics on the screen and sound. In the future, we may see more exotic devices for output for games, but for the moment these are the two most common. Graphics are the most important of the two, perhaps because we humans are more oriented towards vision than hearing. For this reason, many game designers devote a large portion of their energy towards the design of quality displays. Indeed, some designers go so far as to design the display first and let the game develop from the display, as extreme an example of goalless design as ever there could be. Don’t make the common mistake of creating cute graphics solely to show off your ability to create cute graphics. Graphics are there for a reason: to communicate. Use graphics to communicate to the user forcefully and with feeling, and for no other reason. Plan functional, meaningful

The Art of Computer Game Design


graphics that convey the critical game information while supporting the fantasy of the game. Don’t use graphics tricks as a crutch for a bad game design. If the game is dull and boring, no amount of graphics gift-wrapping is going to fix it. The worst examples of this mistake are the games that alternate boring game segments with cute but meaningless graphics displays. Use of sound should follow the same rules: use it to tell the player what’s going on in the game. The only place where striking but uninformative graphics and sound can be useful is at the beginning of the game, and then only if they help to establish the mood or tone of the game. Storyboards are a graphics design tool that tempt many game designers, for they are a well-developed technology from the film industry. They are not appropriate to games, because storyboards are an intrinsically sequential technology. Games are not sequential, they are branching tree structures. The game designer who uses an intrinsically sequential tool risks having her designs made subtly sequential. The tool shapes the mind of its user; the saw suggests that we cut wood, and the freeway suggests that we drive wherever it takes us, not where we choose to go. In like manner does a storyboard impress its sequentiality upon our games. Devote special care to the input structure of the game. The input structure is the player’s tactile contact with the game; people attach deep significance to touch, so touch must be a rewarding experience for them. Have you ever noticed the tremendous importance programmers attach to the feel of a keyboard? Remember that players will do the same thing with your game. A case in point is provided by the games JAWBREAKER and MOUSKATTACK (trademarks of On-Line Systems). In both games the joystick entry routine admits an unfortunate ambiguity when a diagonal move is entered. This gives the player the impression that the joystick is unresponsive. I have seen players slam down the joystick in frustration and swear that they would never play the damn thing again. Remember this well as you plan your input structure: will your input structure frustrate and anger your players? The input structure lies at the heart of a fundamental dilemma all game designers must face. An excellent game allows the player to interact heavily with his opponent, to invest a great deal of his personality into the game. This requires that the game offer the player a large number of meaningful options, enough options that the player can express the nuances of his personality through the choices he makes. Yet, decisions must be inputted, and a large number of options seem to require an extensive and complicated input structure, which could well be intimidating to the player. Our dilemma, then, is that an excellent game seems to require a hulking input structure. The dilemma is resolved through the designer’s creativity in designing a clean input structure that allows many options. This does not come easily. Many schemes must be considered and rejected before a satisfactory solution is found. Yet, such a solution is often possible. In designing SCRAM, a nuclear power plant game, I faced the following problem: how can a player control an entire nuclear power plant with only a joystick? At first glance, the task seems hopeless. Nevertheless, the solution I eventually discovered works very well. The player moves a cursor through the plant

The Art of Computer Game Design


display. With the cursor adjacent to a piece of controllable equipment, the player presses the joystick button and pushes the stick up to turn on or increase power, and down to turn off or decrease power. The system is simple and easily understood once the player has seen it. There is a general solution, at the theoretical level, to the dilemma of option richness versus input cleanliness; I call this solution "the webwork". To design a webwork game, we start with a small number of pieces. We then define a relationship that applies to all pairs of pieces. The set of relationships between pieces constitutes a webwork. The webwork can easily become quite complex, yet few pieces are required to create the webwork. In general, the number of pairwise relationships is equal to N*(N-1), where N is the number of pieces. Thus, four pieces can generate 12 pairings, 8 pieces can generate 56 pairings, and 16 pieces can generate 240 pairings. With fewer pieces to manipulate the player faces fewer I/O problems without sacrificing a rich set of relationships in the game. Backgammon illustrates the simplicity and power of webwork games. Backgammon has only 30 pieces and 26 positions for them to occupy. The relationships between pieces are fairly simple and are expressed through the ability to move and bump. Yet, on any given move, each piece has an offensive, defensive, blocking, or blocked relationship with most of the other pieces on the board. This is partly because almost every other board position in front of the piece can be reached, given the right die roll. It is no accident that the length of the playing area (24 steps) is exactly equal to the maximum die roll. It had to be that way to squeeze all of the pieces into range of each other, thereby maximizing the number of significant pairwise relationships. Most webwork games rely on spatially expressed webworks; these are easy to depict and easy for the player to visualize. Few games have non-spatial webworks; my own GOSSIP is one such game. Curiously, GOSSIP uses a spatial webwork for its internal computations even though the game webwork is non-spatial. This may imply that game webworks are intrinsically spatial; it may equally well imply that I cannot shake my mind-set free from spatial webworks. The choice of input device is an important design decision. I maintain that a good game designer should eschew the use of the keyboard for input and restrict herself to a single simple device, such as a joystick, paddle, or mouse. The value of these devices does not arise from any direct superiority over the keyboard, but rather in the discipline they impose on the designer. Simple input devices go hand-in-hand with simple input structures. Complex input devices encourage complex input structures. The I/O structure is the most important of the three structures in a computer game, for it is the face of the game that the player sees. It is the vehicle of interaction for the game. It is also the most difficult of the three structures to design, demanding both human sensitivity and complete technical mastery of the computer. Give it the care it deserves.

The Art of Computer Game Design


Game Structure
The central problem in designing the game structure is figuring out how to distill the fantasy of the goal and topic into a workable system. The game designer must identify some key element from the topic environment and build the game around that key element. This key element must be central to the topic, representative or symbolic of the issues addressed in the game, manipulable, and understandable. For example, in EASTERN FRONT 1941, I started with the enormous complexity of modern warfare and extracted a key element: movement. Movement dictates the dispositions of the military units. Moving into an enemy’s position initiates combat with him. Moving behind him disrupts his supplies and blocks his retreat routs. Moving into a city captures it. Movement is not equitable with all aspects of war; it is, instead, the key element through which many other aspects of war are expressible. It is easily manipulable and immediately understandable. A more difficult design challenge came from the game GOSSIP. This game addresses social relationships. The enormous complexity of the subject matter and the intricate twists and turns of human interaction together suggest that the subject is beyond treatment in a game. After much thought I was able to isolate a key element: the "statement of affinity". One way or another, many of our social interactions boil down to one of two declarations: a first-person statement of feeling ("I rather like Sandra"), and a third-person statement ("Well, Tom told me that he doesn’t like Sandra one bit"). The key element encapsulates the grander array of human interactions rather well. It is easily manipulable; indeed, it is quantifiable. And it is quite understandable. The isolation of the statement of affinity as the key element of human interaction made possible the game GOSSIP. The nature of manipulability assumes tremendous importance to the success of the game. The key element must be manipulable, but in a very specific set of ways. It must be expressively manipulable; that is, it must allow the player to express himself, to do the things that he wants or needs to do to experience the fantasy of the game. For example, in a combat game, shooting is almost always a key element. If the player’s freedom to shoot is heavily restricted, the player cannot live the fantasy. At the same time, the manipulability must be concise. To use the combat game example again, if the player is required to declare the amount of gunpowder to be expended on each shot, he may well find the manipulability a hindrance to the game. The manipulability must be meaningful to the fantasies of the game. Finally, the manipulability must be focused: the options from which the player chooses while manipulating the key element must be closely related. For example, in the game GOSSIP, the key element (statement of affinity) assumes a linear sequence of values ranging from hatred through love. ENERGY CZAR violates this principle by requiring the player to choose from a large, disconnected set of options. Menu structures and use of the keyboard both arise from unfocussed key elements.

The Art of Computer Game Design


Many games employ multiple key elements. For example, most combat games include both movement and shooting. This is not necessarily bad; if both key elements are kept simple, or if one key element retains primacy, the game can be successful. However, too many key elements violating too many of these principles will rob the game of its focus. Your main problem with creating the I/O structure is overcoming constraints; your main problem with creating the game structure is realizing possibilities. Your previous work with the I/O structure defines the limitations on the structure of the game. You can take more liberties with the internal structure because the player will not directly encounter it. For example, for the game TACTICS I developed a very complex combat algorithm that realistically calculates the effects of armor-piercing shot. The complexity of this algorithm would have confused the player had I tried to explain it. But the player does not need to understand the internal workings of the algorithm; he need only grasp its effects. I therefore did not feel constrained to design a simple-minded and intuitively obvious algorithm. Concentrate an providing enough color to guarantee that the game will convey the authentic feel of reality. Keep your sense of proportion while adding details. It will do your game no good to provide exquisite detail and accuracy in one sphere while overlooking the most fundamental elements in another sphere. A very common mistake many designers make is to pile too many game features onto the game structure. In so doing, they create an overly intricate game, a dirty game. As I discussed in Chapter 4, dirt is undesirable; a game is a structure that must fit together cleanly and well, not a brushpile. Dirt creates a second problem not mentioned in Chapter 4: it gums up the I/O structure of the game. For example, the long-range scan feature of STAR RAIDERS does provide some nice additional capabilities, but it adds another keystroke to be memorized by the player. That’s dirty input. Fortunately this problem is overridden in STAR RAIDERS, because the fantasy puts the player at the controls of a starship, and so the player finds the intricacy of the control layout a supporting element of the fantasy rather than a hindrance. In most games, you may well be forced to give up nice elements in the game structure in order to maintain the quality of the I/O structure. On the other hand, you may be forced to go back and change the I/O structure to incorporate a game feature you are unwilling to abandon. If you do so, do not simply tack on a now command; rethink the entire I/O structure and modify it so that the new command fits well with the rest of the I/O structure. Designing the game structure is emotionally very different from designing the I/O structure. While designing the I/O structure, the designer must thread a precarious path between the Scylla of expressive power and the Charybdis of expressive clarity, even while the storms of hardware limitations toss her design to and fro. While designing the game structure, the designer finds herself on a placid sea stretching flat to the horizon. The challenge taunting her now is "Where do you go?"

The Art of Computer Game Design


Program Structure
The program structure is the third object of your design attentions. This structure is the vehicle which translates the I/O structure and game structure into a real product. One of the most important elements of the program structure is the memory map. You must allocate chunks of memory for specific tasks. Without such safeguards, you may end up expending excessive quantities of memory on minor functions, and having insufficient memory remaining for important tasks. Definitions of critical variables and subroutines are also necessary. Finally, some documentation on program flow is important. Use flow charts or Warnier-Orr diagrams or whatever suits your fancy. This book is not primarily concerned with programming; if you need guidance on program development, consult any of the many excellent books on program development. Top

Evaluation of the Design
You now have three structures in hand: the I/O structure, the game structure, and the program structure. You are satisfied that all three structures will work and that they are compatible with each other. The next stop in the design phase is to evaluate the overall design for the most common design flaws that plague games. The first and most important question is: does this design satisfy my design goals? Does it do what I want it to do? Will the player really experience what I want him to experience? If you are satisfied that the design does pass this crucial test, proceed to the next test. Examine the stability of the game structure. Remember that a game is a dynamic process. Are there any circumstances in which the game could get out of control? For example, if the game has money in it, could a situation arise in which the player finds himself the owner of ridiculously large amounts of money? In short, does the game structure guarantee reasonable upper and lower bounds on all values? If not, re-examine the game structure carefully with an eye to structural changes that will right the situation. If you have no other options, you may be obliged to put them in by brute force (e.g., "IF MONEY > 10000 THEN MONEY 10000") Now probe the design for unanticipated shortcuts to victory. A player who can find a way to guarantee victory with little effort on his part will not derive the full benefit of your game. Insure that all unintended shortcuts are blocked so that the player must experience those processes that you want him to experience. Any blocks you place must be unobtrusive and reasonable. The player must never notice that he is being shepherded down the primrose path. An example of obtrusive blocking comes from the game WAR IN THE EAST (trademark of Simulations Publications, Inc). This wargame deals with the Eastern Front in World War 11. The Germans blitzed deep into Russia but their advance ground to a halt before Moscow. To simulate this the designers gave the Germans an overwhelming superiority but also gave them a supply noose whose length was carefully calculated to insure that the Germans would be jerked to a dead halt just outside Moscow. The effect was correct, but the means of achieving it were too obvious, too obtrusive.

The Art of Computer Game Design


The last and most crucial decision is the decision to abort the game or proceed. It should be made now, before you commit to programming the game. Do not hesitate to abort the game now; even if you abort now you will still have I earned a great deal and can say that the effort was worthwhile. A decision to give up at a later stage will entail a real loss, so give this option careful consideration now while you can still do it without major loss. Abort if the game no longer excites you. Abort if you have doubts about its likelihood of success. Abort if you are unsure that you can successfully implement it. I have in my files nearly a hundred game ideas; of these, I have explored at length some 30 to 40. Of these, all but eight were aborted in the design stage.

If the game has made it this far, you are now ready to commit your ideas to paper. Until now your documentation has been sketchy, more along the lines of notes and doodles than documents. Now you are ready to prepare your complete game documentation. First, commit all of your design results from the previous phase to paper. Define the I/O structure and the internal game structure. The tone of this documentation should emphasize the player’s experience rather than technical considerations. Compare this first set of documents with your preliminary program structure notes; adjust the program structure documents if necessary.

This is the easiest of all the phases. Programming itself is straightforward and tedious work, requiring attention to detail more than anything else. Seldom has a game failed solely because the programmer lacked the requisite programming skills. Games have failed to live up to their potential because the programmer did not expend enough effort, or rushed the job, or didn’t bother to write in assembly language, but in few cases has talent or lack of it been the crucial factor in the programming of a game; rather, effort or lack of it is most often the responsible factor. If you place all of your self-respect eggs in the programming basket, I suggest that you get out of game design and work in systems programming. Otherwise, write the code and debug it.

Ideally, playtesting is a process that yields information used to polish and refine the game design. In practice, playtesting often reveals fundamental design and programming problems that require major efforts to correct. Thus, playtesting is often interwoven with a certain amount of program debugging. Sometimes playtesting reveals that the game is too seriously flawed to save. A nonfatal, correctable flaw is usually a matter of insufficiency or excess: not enough color, too many pieces, not enough action, too much computation required of the player. A fatal flaw arises from a fundamental conflict between two important elements of the game whose incompatibility was not foreseen.

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You must have the courage to trash a game with such a fatal flaw. Patching after the game is programmed can only achieve limited gains; if the game is badly deformed, abortion is preferable to surgery. If playtesting reveals serious but not fatal problems, you must very carefully weigh your options. Do not succumb to the temptation to fall back on a quick and dirty patch job. Many times the problem that is discovered in playtesting is really only a symptom of a more fundamental design flaw. Be analytical; determine the essence of the problem. Once you have determined the true nature of the problem, take plenty of time to devise a variety of solutions. Don’t rush this process; sometimes the ideal solution comes from an unexpected angle. Choose a solution for its promise of furthering the faithfulness of the game to your goals. Do not opt for the easiest solution, but the solution that best meets your goals. For example, while designing EASTERN FRONT 1941, I ran into a severe problem with unit counts: there were far too many units for the player to control conveniently. After wasting much time trying to devise ways to shrink the map or directly reduce the number of units, I eventually stumbled upon zones of control, a standard wargaming technique that extends the effective size of a unit. The inclusion of zones of control in the game not only solved the unit count problem; it also made the logistics rules more significant and gave the game a richer set of strategies. I set out with the narrow goal of reducing the unit count, but I found an improvement with much broader implications. If your initial design was well-developed (or you are just plain lucky) the game will not face such crises; instead, the problems you will face will be problems of polish. All of the little things that make a game go will be out of tune, and the game will move like a drunken dinosaur instead of the lithe leopard you had envisioned. Tuning the game will take many weeks of work. For the short term you can scrimp on the tuning while you are working on other problems, for tuning the game requires delicate adjustments of all the game factors; any other changes will only throw off the tune. Therefore, defer final tuning work until the very end of the polishing stage. There are actually two forms of playtesting. The first is your own playtesting done in the final stages of debugging. The second form comes later when you turn over the game to other playtesters. The salient-difference between the two lies in the nature of the bugs exposed. Your own playtesting should reveal and eliminate all program bugs (arising from flaws in the program structure) and many of the game bugs (arising from flaws in the game structure). The game you give to the playtesters should be free of program bugs; they should discover only bugs in the game structure. There is no point in showing an incomplete game to playtesters, and indeed there is a danger in contaminating their objectivity by showing them a version of the game too early. But the time will come when you feel that the game is very close to completion, and your own stock of ideas for improvements is dwindling. This is the time to show the game to a few select playtesters.

The Art of Computer Game Design


Playtesters must be selected and used with great care. You cannot simply grab a few friends and ask them what they think of the game. You need playtesters who possess a deep familiarity with games, playtesters who can analyze and criticize your game with some basis of experience. Ideally the playtesters would themselves be game designers, for they would then share your appreciation for the trade-offs essential to good game design. You should also know the player well, both his personality and his game taste. You should never use more than five or six playtesters. A surplus of playtesters only insures that you will not be able to assess carefully the reaction of each playtester. A variety of other systems have been used for playtesting. Most rely on gathering large groups of "real people" and assessing their reactions to the game. I have little respect for such systems. Although they are scientific, objective, and democratic, they seldom yield useful design information, for consumers make lousy critics. The suggestions they make are inane and impractical; they don’t know enough about computers or games to make practical suggestions. Such methods may well work with detergent and shaving cream, but I very much doubt that any great movie, book, or song was created through market research of this kind. I will concede that such methods can prove to be a useful way to guide the mass production of cheap games by designers of limited talents; this book is not directed to persons of such a mentality. The playtesters will need a preliminary manual for the game. It need not be a finished product any more than the game itself---just enough orientation information to get the playtester going with the game. Make sure that there is enough in the manual that the playtester doesn’t waste time critiquing problems of the game that will be solved by the manual. Do not sit down with the playtester in advance and coach him through the game; you will only contaminate his objectivity. The playtester’s first reaction to the game is your best feedback on the success of the manual . Let the playtester experiment with the game for perhaps a week before you meet with him. Do not ask the playtester to keep lengthy written records of play performance; he won’t do it. Instead, include in the manual a few suggestions about potential problems that worry you. The most for which you should ask in writing is a simple record of game options selected and subsequent scores. Schedule along interview with the playtester after he has had enough time to digest the game. Come to the interview prepared with a set of standard questions that you ask all playtesters. Do not lead the playtester’s answers and don’t solicit praise. Your job is to find flaws; accolades come later. While it is more scientific to use a third person to conduct the interview (thereby assuring more honest answers), this imposes a middleman between you and your playtesters. I prefer to get the information directly from the playtester. I also prefer to take a very negative tack during the interview, encouraging the playtester to criticize the game along with me and to suggest means of improving it. Playtesters’ criticisms are difficult to evaluate. Most criticisms must be rejected for a variety of reasons. Some are incompatible with your goals; some are not achievable in the-memory space remaining. Some are reasonable, but would require major software surgery incommensurate with

The Art of Computer Game Design


the gains offered. Do not hesitate to reject 90% of the suggestions made. The remaining 10% are right; waste no time implementing them. How do you tell the good 10%? This is the stuff of wisdom; I certainly don’t know. The final stage of the design cycle is devoted to polishing the game. The polishing stage is actually concurrent with the later stages of playtesting and may involve several iterations with the playtesters. This stage is critical; the designer has been working on the game for a long time by now and the luster of the new design has worn off. It is now only a big job that should have been finished months ago. The playtesters love it, the publisher loves it and wants it right now, and the designer is sick of it. The urge to dump the damn thing is overpowering. Resist this urge; press on relentlessly and polish, polish, polish. Keep testing the game, fine-tuning it, and adding tiny embellishments to it. Once it’s out the door, it’s gone forever. Every single game I have done has followed the same pattern: I polished the game until I was sick of it and never wanted to see it again. When at last I sent the game out, I rejoiced; I was free of that dog at last. Within a month I was regretting my impatience and wishing I could have a chance to clean up that one embarrassing bug that I had never noticed. Within three months my regret had turned into shame as I discovered or was told of many more bugs. I have programs out there whose patrimony I hope never becomes widely known. One of the last tasks you must perform before releasing the game is the preparation of a game manual. Manuals are frequently given short shrift by just about everybody associated with computer games. This is a serious mistake, for the manual is a vital element in the overall game package. A computer has many limitations; some can be overcome with a good manual. Much of the static information associated with a game can be presented in a manual. The manual is also an excellent place to add fantasy support elements such as pictures and background stories. Finally, a well-written manual will clear up many of the misunderstandings that often arise during a game. You must write your own manual for the game, no matter how poor a writer you are, and even if a professional writer will prepare the final manual. The attempt to write your own manual will increase your respect for the skills of the professional writer, making it more likely that you will have a productive relationship with the writer. Writing your own manual will also provide feedback on the cleanliness of the game design. Clumsy designs are hard to describe, while clean designs are easier to describe. Finally, your own manual will be a useful source document for the professional writer. You should be prepared for the writer to throw out your manual and start all over---a good writer would rather create a new manual than polish an amateur's crude efforts. You must cater to the writer’s needs, answering all his questions as completely as possible. Only a close and supportive relationship between designer and writer can produce an excellent manual.

Once the program is out, brace yourself for the critics. They will get their filthy hands on your lovely game and do the most terrible things to it. They will play it without reading the rules.

The Art of Computer Game Design


If it’s a strategic game, they will castigate it for being insufficiently exciting; if it’s an S&A game, they will find it intellectually deficient. They will divine imaginary technical flaws and speculate incorrectly on your deep psychological hang-ups that led you to produce such a game. One critic of mine concluded that TANKTICS was obviously slapped together on a rush schedule; actually, the time between first efforts and final publication was five years and two months. Another roasted ENERGY CZAR (an energy economics educational simulation) because it wasn’t as exciting as his favorite arcade game. Don’t let these critics affect you. Most critics are far less qualified to criticize programs than you are to write them. A very few critics with the larger publications are quite thoughtful; you should pay attention to their comments. With most critics, though, you should pay heed only to views shared by three or more independent critics. Remember also that even a good critic will roast you if your goal is not to his taste. The public is another matter. If they don’t buy your game, you lose two ways: first, you or your employer make little money on the game; and second, you don’t reach as many people with your message. It doesn’t matter how beautiful your message is-if nobody listens to it, you have failed as an artist. One failure is nothing to worry about; every artist bombs occasionally. Two failures in a row are bad; three should initiate a serious reconsideration of artistic values. Are you willing to be a noble and starving artist, or a somewhat wealthier artisan? Look within your heart, long and hard. If deep down inside you know that you met your goals, then ignore the critics and the public.

The Art of Computer Game Design


CHAPTER SIX Design Techniques and Ideals


very artist develops her own special techniques and ideals for the execution of her art. The painter worries about brush strokes, mixing of paint, and texture; the musical composer learns techniques of orchestration, timing, and counterpoint. The game designer also

acquires a variety of specialized skills, techniques, and ideals for the execution of her craft. In this chapter I will describe some of the techniques that I use. Top

A solitaire game pits the human player against the computer. The computer and the human are very different creatures; where human thought processes are diffuse, associative, and integrated, the machine’s thought processes are direct, linear, and arithmetic. This creates a problem. A computer game is created for the benefit of the human, and therefore is cast in the intellectual territory of the human, not that of the computer. This puts the computer at a natural disadvantage. Although the computer could easily whip the human in games involving computation, sorting, or similar functions, such games would be of little interest to the human player. The computer must play on the human’s home turf, something it does with great difficulty. How do we design the game to challenge the human? Four techniques are available: vast resources, artificial smarts, limited information, and pace.

Vast Resources
This is by far the most heavily used technique for balancing a game. The computer is provided with immense resources that it uses stupidly. These resources may consist of large numbers of opponents that operate with a rudimentary intelligence. Many games use this ploy: SPACE INVADERS, MISSILE COMMAND, ASTEROIDS, CENTIPEDE, and TEMPEST are some of the more popular games to use this technique. It is also possible to equip the computer with a small number of opponents that are themselves more powerful than the human player’s units, such as the supertanks in BATTLEZONE. The effect in both cases is the same: the human player’s advantage in intelligence is offset by the computer’s material advantages. This approach has two benefits. First, it gives the conflict between the human and the computer a David versus Goliath air. Most people would rather win as apparent underdog than as equal. Second, this approach is the easiest to implement. Providing artificial intelligence for the computer’s players can be difficult, but repeating a process for many computer players takes little more than a simple loop. Of course, the ease of implementing this solution carries a disadvantage: everybody else does it. We are kne

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