FUNDAMENTALS OF GAME DESIGN, SECOND EDITION

Static and Dynamic Equilibrium

It's possible to design a system in such a way that, left alone, it enters a state of equilibrium. Static equilibrium is a state in which the amounts of resources pro­duced and consumed remain constantly the same: Resources flow steadily around without any significant change anywhere. Dynamic equilibrium occurs when the system fluctuates through a cycle. It's constantly changing, but it eventually returns to a starting point and begins again.

Here's an example of static equilibrium. Suppose you have a miller grinding wheat to make flour and a baker baking bread from the flour. If the bakery consumes the flour at exactly the same rate at which the mill produces it, then the amount of flour in the world at any one time will remain static. If you then upset the system by stopping the bakery for a while, the flour will build up. When the bakery restarts, the amount of flour available will be static at the new level. The system returns to static equilibrium because the key factors—the production and con­sumption rates of the mill and the bakery—have not changed (see Figure 10.4).

Now let's suppose that only one person does both jobs. She mills enough to bake three loaves of bread; then she bakes the three loaves; then she mills again; and so on. This is an example of dynamic equilibrium: Conditions are changing all the time, but they always return to the same state after a while because the process is cyclic. If we tell the woman to stop baking and only mill for a while, and then re­sume baking later, again the flour builds up. When she resumes baking, the system settles into a new state of dynamic equilibrium (see Figure 10.5).

When a game such as a construction and management simulation settles into a static equilibrium, players can easily judge the effect of their actions on the system by making one small change and watching the results. This makes the game easy to learn and play. Dynamic equilibrium is more difficult for players to handle. With the system in constant flux, it's hard to tell whether the changes players see result from a natural process or from something they've done.

Settling into a state of equilibrium, static or dynamic, takes the pressure off the player. She can simply watch the game run for a while and make adjustments when she feels like it. Some construction and management simulations do work that way, but most give the player more of a challenge. Rather than settling into equilibrium, the designers build in a factor that requires the player to take action to prevent the system from running out of some needed resource. To use our milling-baking met­aphor, perhaps the player has to take action to keep the mill supplied with wheat. If the player doesn't keep an eye on the wheat supply, both milling and baking come to a halt. In Age of Empires, farms produce food automatically, but after a while they stop working and the player must intervene to rebuild them. In SimCity, the roads wear out and the player has to repair them.

Whether your system settles into equilibrium or runs down without player action, one thing is certain: The player should always have to do something to obtain growth—he should have to press on the gas pedal of your game, as it were. If the

system can grow constructively and profitably of its own accord, there's no reason for the player to interfere. This is the player's primary challenge: figuring out how to produce growth using the many (metaphorical) levers and knobs that you pro­vide via the core mechanics. In effect, the player is himself an element of the economy, and growth depends on his active participation.