[Is there a defining theory for game design? Kalisto and 10tacle designer Bura tries to create a 'periodic table of elements' for creating games - from surprise through dread and beyond.]

This is a very exciting time to be a video game designer.

Video game design is evolving from a barely understood activity done by genius designers driven by their gut feelings, to a craft with shared techniques and methodologies. A common vocabulary cobbled from various fields (interface design, psychology, complex systems, physics, etc.) is slowly emerging. Successes and failures are analyzed...

But it's still a big mess, a large toolbox where any designer can find the right tool to confirm exactly what he believes in. There are no universally accepted truths, only opinions about what makes a great game, whether or not video games are an art form or whether there is an effective method to teach video game design.

We lack ways to compare games in an objective manner, ways to describe them in a shared language. Without proper description, there can be no true understanding. Success in video games still hinges on applying traditional techniques, copying, marketing, luck, or genius. And even if success is achieved, there's no guarantee that we can know why it happened.

Arts and sciences have rules and laws, not just techniques. But what are the rules of video game design?

Where is our redox law? Our perspective rule? Our theory of relativity?

Where are the formal tools we can use to better understand, analyze, and improve games?

How big is the game design space and can we identify its virgin territories?

What are the rules we can bend or break to create totally new experiences?

This article presents a theory of what video game game design is and explains how to find some of these rules.

Caveat: If I sound pedantic or over-confident in this article, please prefix any affirmation I make with "I modestly believe without being able to prove that..." This work has generated many hours of doubt and self-doubt. I do not pretend to teach anyone the definitive meaning of trust, catching-up, fear, or of collecting a power-up. This is an ongoing work, as the article's version number - 1.0.4 - attests. If you disagree with me, please tell me why and I'm sure you'll be convincing enough to change my mind.

That said, let's start with easy questions that have clear answers: "What is game design?" and "What is a good game?"

What is Game Design?

Players don't play to complete games, just as readers don't read to finish books. Players play to feel emotions. Game design is experience crafting for the purpose of emotion engineering.

Game design is intrinsically hard because its output is an interactive system that is twice removed from its goal. The game designer produces rules for interaction that, with the participation of the player, generate game states that themselves induce emotions in the player.

Note: In Emotional Design, Donald Norman describes three different levels of experience processing: visceral (how it makes the person having the experience feel), behavioral (how well it suits its purpose or function), and reflective (how it affects the person’s self-image). Games can have a behavioral aspect, from being a learning tool to a systemic demonstration of a concept. This article focuses on the other two aspects: how games can have an emotional impact on their players.

If we can describe a given game state using a set of gameplay variables, we get the following cycle:

Interactions between the player and the game produce changes in the gameplay variables. For instance, finding a heart container in Zelda and getting a bigger full health bar obviously changes something in the game state. We'll explore below what this could be.

Variations or stability of these variables induce emotions in the player. For instance, having a bigger full health bar could make him more confident.

Player's emotions influence how he interacts with the game. For instance, being confident might make him take more risks; pride might keep him chasing a high score; or boredom might make him stop playing altogether.

Some of these emotions are the result of a carefully crafted sequence of events. Others stem from the normal moment-to-moment interaction with the game. Since the players and their playing experiences are so different from one another, one cannot guarantee that a given player will feel a given emotion at a given point in a game. However, from our understanding of physiology, psychology, cognition, or culture, we can identify situations that create the proper context for the expression of such an emotion.

Note: This article is not about creating emotions with the content, the subject matter, or the story, but through interactions with the game alone. Indeed, these are integral parts of the whole - emotions are enhanced by the appropriate setting or story - but the subject has been talked about at length by better qualified people elsewhere. So I'll skip this for now.

Game design works backwards around this cycle, trying to predict player emotions from changes in the interactive system. But our knowledge of the dependencies between interaction and emotion is so sparse that most changes require testing. Testing in part requires implementing the changes, which costs time and money. Thus, in a professional setting where budget is an issue, game design innovation can quickly become a risk.