Every videogame creates some kind of world, be it one that somewhat resembles the real world or an abstract puzzle world. The definition of this world consists of the kinds of objects that can inhabit it and how those objects can interact with one another.

The first part of this definition can be thought of as a taxonomy, or a way of organizing objects into categories and subcategories. For example, an object taxonomy for Pac-Man might look something like this:

There are five major classes of objects: mazes, ghosts, dots, fruit, and Pac-Man himself. Each class can give rise to many different objects with the same basic properties, as in mazes with different configurations and fruits with different bonus values.

Likewise, a class of objects can have subclasses that inherit the properties of the parent class while adding some of their own. The four ghosts all interact with Pac-Man and the maze in the same way, but their movement follows different rules (or so Wikipedia tells me – I’m no Pac-Man expert).

In general, there is more analysis of videogames centered around the rules and potential actions of the game world, but looking at how objects relate to one another can also tell you a lot about a game.

Take a minor frustration from Final Fantasy VII. When you fight the ninja girl Yuffie, she has all these neat wave attacks that immediately disappear when she later joins your party. This suggests that, in this game, “enemies” and “allies” are separate classes that don’t lend themselves to easy conversion. This is not the case in some other Japanese RPGs, such as Chrono Cross; here, when former enemies join your party, they behave pretty much the same. “Enemies” and “allies” are only slightly distinct subclasses of “combatants.”

This difference has some major implications for gameplay. For one thing, Chrono Cross has a doppelganger character who can take on the abilities of an opponent, which wouldn’t be possible in FF7. More importantly, it affects your ability to read your opponents. Knowing an enemy is the same kind of thing as you helps you to predict what it might do more intelligently. In games like FF7, you have no idea what the enemy is capable of, so battles are more unpredictable.

Not that one way or the other is better, but it is a meaningful difference, and a sign that looking at how a game world organizes objects can be as revealing as examining its rules.