FUNDAMENTALS OF GAME DESIGN, SECOND EDITION

The Internal Economy

An economy is a system in which resources and entities are produced, consumed, and exchanged in quantifiable amounts. Most games have an internal economy, though the complexity and importance of the internal economy varies consider­ably from genre to genre. Chapter 18, "Construction and Management Simulations," provides more discussion of internal economies.

A game designer spends part of her time designing and tuning her game's econ­omy, and the more complex the economy, the more time she needs to spend. This section introduces aspects of an internal economy, which it explains by reference to both a simple action game (a shooter) and a complex game (a construction and management simulation).

Sources

If a resource or entity can come into the game world having not been there before, the mechanic by which it arrives is called a source.

In a simple shooter, the game begins with some resources, such as enemies, already in the game world, but more enemies may appear at spawn points. A spawn point is a designated location where the core mechanics insert new resources into the game world and therefore into the economy. Enemies are part of the economy, a resource that is produced at spawn points and consumed by conflict with the avatar. Each spawn point is governed by a mechanic that specifies its location, what kind of resource it generates (spawn points in shooters can also produce weapons, ammuni­tion, or health packs), and at what frequency.

Sources often produce resources automatically (or at least produce resources auto­matically once the player starts them going, for example, by building a factory).

You will need to define a production rate, either fixed or variable, and different sources may produce the same resource at different rates. In The Settlers games, riv­ers produce fish at a constant rate. A mechanic also defines the maximum number
of fish that may be in a river at any one time, so the river stops producing fish when it gets full.

Sources can be global mechanics: A mechanism that pays the player interest at reg­ular intervals on the money he owns would be one example. An interest-payment mechanism applies throughout the game regardless of anything else, so it is global. Sources can also make up part of the mechanics governing the behavior of entities. In The Settlers, a stream that produces fish is an entity, one of whose attributes is the number of fish it contains.

Sources can be limited or unlimited. In Monopoly, the "Go" square constitutes an unlimited source—according to the rules, it can never run out of money. (If the bank runs low, the banker may make more money by writing on paper.) But the collection of houses and hotels stored in the bank is a limited source: Once the banker sells all the houses and hotels, no more may come into the game. The stream in The Settlers is an unlimited source of fish. Although it can be temporarily empty if too many fishermen are catching fish from it, it goes on producing fish until it is full, as long as the game is running.