Real Interactivity in Interactive Entertainment

Overview

This article discusses some of the aesthetic and philosophical issues of game design as well as outlining some of the challenges of the modern interactive entertainment designer. Particular attention is given to the nature of interactivity. Methods are discussed for maximizing the interactivity of entertainment experiences. Comparisons are drawn between non-linear, interactive entertainment and sequential story- based entertainment forms.

Interactivity

The task of a computer game designer is to create an experience, using a computer, which is interesting and fun for the player. The designer must create a system of behavior such that the player enjoys interacting with that system and will continue to interact with it.

The key word is interact. The computer is by nature an active, participatory medium. Players who prefer a passive enjoyment can get a far superior experience for less cost through the medium of video tape or laser disc.

The modern computer game is an audio-visual “engine” capable of keeping an internal model of some dynamic system, and can effectively present one or more facets of that model on the player’s graphic display, while accepting inputs from that player that affect how the system behaves. Unlike a “real” application, however, a game often deliberately hides certain pieces of information about its internal state, working against the user to create a greater challenge.

Game engines tend to evolve over time. Each time the publisher creates a sequel, spin-off or related product, the designer usually has the opportunity to refine his or her previous work, as well as creating a foundation for more ambitious future works. Some of these programs are quite sophisticated, and borrow algorithms and techniques from many other areas of computer science, all in the service of some particular aesthetic result.

Making the game interesting is the designer’s most important task. Part of this involves creating a set of design documents which specify the rules and parameters which determine the behavior of the game’s internal model. This specification can come in a variety of forms, depending on the nature of the game and which company you’re working for. These forms could include a traditional Hollywood-style “script”, source code in either C or a custom game-specific language, equations for a fuzzy logic engine, or even a set of rules for a cellular automata.

Degrees of Freedom

From a gaming perspective, the more interactive the system is, the better. However, it is sometimes unclear what the definition of Interactivity really is. Lets take that reducto ad absurdum of interactivity, the VCR. Is a VCR interactive? After all, you can stop the tape, rewind it, and such. While these are useful capabilities, they aren’t very interesting or fun from the user’s point of view. Since we want our experience to be both interesting and fun, it’s important to distinguish fundamentally between what our game product does and what a VCR does.

One quality which a VCR lacks is adaptability. While it responds to the user’s commands, it’s memory of those commands is limited to a very simple internal state, and it keeps no record of the “style” in which those commands were invoked. A computer game can potentially adapt to the user’s actions, changing its strategy and rules based on what has gone before.

Another distinction is a VCR only gives us control over one axis, that of time. We have no control over the spatial positions of any of the characters or objects in the movie, or even our own point of view. Nor do we have any choice what the characters in the story do or say.

It could safely be said that a product which adapts to the player’s behavior and permits as many degrees of freedom as possible is going to be more interesting than a product that lacks these attributes. Now, it is true that there are a number of other important factors in making a game entertaining, such as balancing the amount of non-obvious behavior of the system, and controlling the rise of the player’s expectations during the course of play. Even more important is the careful omission of “misfeatures” which have been shown to annoy players in previous products. However, this article will focus on making an experience which is as interactive as possible, since that is one of the primary design challenges for the game creator.

Storytelling

For thousands of years, storytelling has been the basis for most of our entertainment forms. From the classic and colorful storyteller in the marketplace, to novels, plays and motion pictures, the involvement of the listener in the emotional trials of a fictional character is a powerful entertainment process. So it would be natural to view the computer medium as yet another opportunity for storytelling, and to think that the “immortal power of storytelling” will create a great software product. Writer Bruce Sterling calls this the “Me an’ my good buddy Bill Shakespeare” argument.

I go to conferences and trade shows where I see many talented young authors who want to “break in” to the interactive entertainment medium. They see computers and CD-ROMs as a medium by which they can express the dramatic situations and interesting characters in their imagination.

Unfortunately, I’ve found that it can be very difficult for an author to make the transition. Most other media forms are linear -- they have a beginning, a middle, and an end. Interactive games represent a multiplicity of paths, each divergently branching to a different experience and hopefully a different conclusion. I’ve worked with some very good novelists who just could not deal with this -- their designs had very few interactive choice points, each having very few possible choices, and the choices often lead to surrealistically nonsensical outcomes.

I believe that on a fundamental level, storytelling and interactivity are exclusive to one another. Interactivity puts the player in charge, storytelling puts the author in charge. Interactivity allows the player to go wherever they want, to do and see whatever they want. Storytelling would dictate that the protagonist be restricted to acting in ways that make sense dramatically. In a novel, it is considered bad for a character to give long-winded explanations, whereas in a computer game this is perfectly acceptable under some conditions. For example, a player might be interested enough in a particular piece of knowledge that they might be unsatisfied with a summary explanation, and so would request further detail on the subject. As long as players have the power to control which explanations are given, and can interrupt them at any time, they are unlikely to get bored.

Another problem with interactive storytelling is that the emotional reverie of the story is broken whenever the player has to get up and “do something.” Making a decision about what the character should do next, which most players approach on a purely intellectual and strategic level, requires a detachment from the mood of the story that most authors would prefer to avoid.

The relationship between the player and the protagonist presents an additional problem for the interactive storyteller. In a story, the character and personality of the protagonist is what makes him or her interesting, and we feel a certain sympathy because of our understanding with the character’s plight. In most games, however, the protagonist becomes our complete surrogate ego, with no intrinsic personality of its own. As such, we are less interested in the protagonist and more concerned with the external environment in which it is embedded.

This is not to say that a game cannot have elements of both storytelling and interactivity. I would model the relationship between the two attributes as a continuum, with storytelling at one and and interactivity at the other:

Figure 1. Continuum of Interactivity. (Note that the placement of titles in the illustration is purely subjective opinion on my part. In general, games which have a highly scripted, sequential structure are placed on the right, and games which lack this are placed on the left.).

For example, “full motion video” (the technique playing video on a computer screen by spooling video data continuously off of a CD-ROM) is in it’s current form a fundamentally sequential medium, and as such inhibits interactivity. Most games that utilize video technology stop the game dead while the video is playing. Only when the video completes is the player allowed to make decisions again.

Game designer Chris Crawford believes that rather than the model of “story,” game designers should be using the using the model of “conversation.” According to Crawford, a conversation requires that both participants must listen, think, and then speak. Ideally, interactive entertainment would be a “conversation in a can” which would not only “speak” eloquently (using multimedia sound and graphics), but “listen” as well. The player would be given an opportunity to “speak” through a rich, well-designed user interface.

Others have suggested that an amusement park may be a more appropriate model for interactive entertainment. In amusement parks, customers can wander around at will, choosing at any time to participate in various attractions. Some attractions have almost no sequential structure at all (shooting gallery), whereas others are a continuously choreographed multimedia experience (Disneyland rides).

It is certainly true that the issue of storytelling is one of the more controversial issues being discussed among professional game designers.

Is there a way to combine storytelling and interactivity completely? I believe so, however the technology for doing so has not yet been developed. Rather than creating a medium for expositing stories to be consumed by a passive audience, this technology would act as a partner to users, allowing them to create their own stories “on the fly” as they experience them.

The ultimate vision of this is researcher Brenda Laurel’s “Artificial Playwright” concept, an expert system which would somehow encode the “laws of drama” into a rule set. This hypothetical system would know about climax and anticlimax, tension and relaxation, and other dramatic principles. As the player moves through the environment, story situations would be generated and developed continuously by the playwright, a sort of software improvisational acting.

Achieving Interactivity with today’s technology

One form of interactivity is referred to as “branching games,” which were first popularized in the “choose your own adventure” novels. In this type of game, the player experiences short, linear story segments. At the end of each segment are a small number (say, 2-4) choices, each leading to a new linear segment, which leads to further choices, and so on. Sometimes the pathways converge; Other times they diverge to different endings. Sometimes they even loop back on themselves again.

The advantage of the branching game is that it allows an author to write a small (or at least finite) number of alternate story paths. A designer can therefore draw upon the talent developed for existing expository media, and the power of storytelling can be applied.

The disadvantage of this technique, however is that the full power of interactivity is diminished -- the player can only choose those paths that have been anticipated by the designer. The problem is even more acute with modern, high-production value graphical adventures. These games use CD-ROM technology to store a massive data set of artwork, music, sound effects, animation on a single disk. A team of artists, animators, writers, and programmers will work for a year or more, mapping out every possible pathway and choice point that the player will want to take, and illustrating every pathway in full cinematic glory.

Of course, since all this graphical data (called “assets” in the trade) are expensive to produce, there is great pressure to cut down on the number of alternative pathways that the player can take. Consequently, there is a strong economic incentive to reduce interactivity to the bare minimum. And since the game can only function on a ROM medium, it means that players are stuck in a mostly “read-only” universe, and are extremely limited in the ways that they can affect the environment.

In the games industry, we have seen a continuing trend in games that are increasingly awesome to look at, and increasingly shallow to play.

Clever Algorithms

The most interactive games, however, do not use the branching technique at all. A typical flight simulator, for example, does not have any discrete choices, the player just goes wherever they want.

Another example of an algorithm-based game with rich interactivity is the highly acclaimed game Sim City. This product simulates the growth and development of an urban metropolis, with the player in the role of city mayor. At each point in the game, the player can perform various operations on the landscape, such as zoning land, demolishing buildings, laying down roads, water mains and electric power lines. Since the game map is large (it appears to be a square 256 grid units on a side), and since the player can perform these operations almost anywhere on the map, the number of possible moves at any given moment in time is clearly immense. Of course, out of that large number of potential moves, probably only several hundred are optimal at any given point. Nevertheless, that is still enough to give the player the feeling of almost complete freedom.

In general, these games use sophisticated algorithms to define behavior of the game rather than preset pathways laid down by a designer. The advantage is clear: The number of possible outcomes is nearly unlimited, given a rich set of inputs.

Algorithms for games don’t just come from game theory, but from many application domains. For example, I have used Lee’s algorithm (a routing algorithm used in electronic CAD programs to plot the optimum pathway for a copper trace on a printed circuit board) to control the movement of animated characters in a fantasy environment. Especially worthy of attention are systems that exhibit emergent behavior, such as genetic algorithms, neural nets, and cellular automata.

Assuming that the creative spark of the designer can just come up with the right algorithm, a game can be created much less expensively than one that utilizes massive data sets.

The primary difficulty with algorithms, then, is not one of economy, but rather one of technology. It can be difficult to invent an algorithm that generates a rich set of behavior that is appropriate for a given game concept. It can be especially difficult to craft an artificial opponent to compete against the player -- in general, algorithms make much better environments than they do opponents.

Algorithms are also poor at simulating realistic human behavior. Even the most sophisticated adventures rely heavily on pre-scripted dialogs for character interaction.

Real People

One of the most interesting and enjoyable interactive systems is the one embodied in the human brain. A real player is often the best choice for interactive opponent, since humans display a larger range of behavior than either massive data sets or algorithms, and can engage in complex social relationships. The latter allows for out-of-context social interaction such as telling jokes about the game, chatting, and emotional reactions when one player defeats another, which can significantly enhance the gaming experience.

The problem with multi-player computer entertainment is opportunity: Many game enthusiasts not only don’t have two computers, they don’t even have two people. At least, within a given household it is likely that the number of people interested in playing a particular genre of computer game will be less than two. Nevertheless, many people in the games industry feel that multi-player games are the most exciting opportunity for the coming decade.

A number of technologies have been developed to try and solve the problem of getting players together, some of which work better than others:

Terminal Sharing: Two players can take turns entering their moves, or each player can choose a different input device and play at the same time. (In some cases, the keyboard is split in half and considered as two input devices). Unfortunately, since both players are in front of the same screen, it makes games that involve hidden information cumbersome.

One-on-One games: A number of sucessful games now include a “serial-play” or “modem-play” option that allows two users to play against each other, each with their own dedicated screen. Of course, lugging one’s machine over to a friend’s house is inconvenient, and playing over the telephone lines ties up the lines as well as eliminating an important channel of social interplay since the players can’t talk to each other over the phone while they are playing the game.

LAN-based games: Many companies have multi-player games on their local area networks. Of course, most companies limit the amount of time one can spend playing on company equipment. Also, since the market is limited, such games tend to be primitive compared to popular commercial games.

Wide-area network games: Most notable are the Multi-User Dungeon games, or “MUD” environments which are very popular on the Internet, as well as their descendants (MUSH, MUCK, MUSE and MOO). These text-based games can be incredibly addicting, since they have had a long history to build up a rich level of detail, as well as a feeling of “aliveness” which single-player adventure games lack. Also, they manage to maintain the social interaction by allowing the players to electronically “chat” at any time during course of play. However, the text-based interface will probably not appeal to a mass audience, even assuming the average consumer could figure out how to get Internet access in the first place. [Author's note: This was written back when the internet was still a "geek thing". My, how time does fly...]

Commercial network games: A number of commercial wide-area network services specialize entirely in games, such as the ImagiNation network and MPGNet. These allow players to have a fully graphical, multi-player experience in their own home, for an hourly fee. High graphical performance is achieved by placing most of the computation in the client program, which runs on the user’s home machine. The client communicates with a central server over the telephone line.

The biggest drawback with this type of game is one of limited bandwidth. Most of these networks use packet-switching technology, which causes a 1 to 3 second delay in returning information to the player, as well as chopping the data stream into clumps rather than a continuous flow. The result is that a smooth, responsive interaction is difficult if not impossible. Thus, “turn-based” games tend to be the rule on these systems rather than real-time action. An additional problem is the potential for “cheating” by clever users who modify their client programs. To prevent this from occurring, the amount and type of information sent to the client must be carefully controlled, which often prevents the most effective use of the available bandwidth.

Location-based entertainment: The most ambitious attempts at multi-player entertainment consist of highly specialized gaming technology clustered into a miniature “theme park” located at a shopping center or mall. Players enter into special “pods” containing a complete audiovisual simulation environment, including wide screens, stereo sound, and mechanical simulation of vibration and acceleration. The advantages are an intense game experience. The disadvantages are that the systems are extremely expensive, and (currently) only located in a few areas. Also, the systems tend to be highly customized for a particular game, so that when players get tired and want a different game, there is still a large capital investment in the old systems. In addition, many pod-based system sonically and visually isolate players from one another, which inhibits the social interaction between players.

Conclusion

While animated graphics and synchronized sound represent significant challenges to the game designer, they are not the primary design problem. Rather, the game design itself -- the set of cause and effect relationships that determine the behavior of the game -- is usually much more difficult to get right.

To create games which the user can enjoy over and over again requires more than traditional storytelling. Techniques for achieving a fully interactive experience, such as sophisticated algorithms or multi-player technologies, can go much further towards creating a unique experience which does not need to compete with traditional expository media.

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Talin@ACM.org

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