FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
Production Mechanisms
Production mechanism describes a class of mechanics that make a resource conveniently available to a player. These include sources that bring the resource directly into the player's hands, but they can also include special buildings, characters, or other facilities that gather resources from the landscape and make them available to the player. Many real-time strategy games employ special characters to perform this function. For instance, in the Command & Conquer series, a harvester vehicle collects a resource called tiberium and carries it to a refinery where it is converted into money that the player can use to buy weapons. The harvester is a production mechanism; the refinery is a converter.
Tangible and Intangible Resources
If a resource possesses physical properties within the game world, such as requiring storage space or transportation, the resource is said to be tangible. On the other hand, if it occupies no physical space and does not have to be transported, it is intangible. In a shooter game, ammunition is tangible—it exists in physical form in the environment, and the avatar has to carry it around. Most construction and management simulations treat money as intangible: It exists as a meaningful resource in the game world but takes up no space and has no particular location.
A number of games treat resources in a mixed fashion, sometimes tangible and sometimes intangible. In Age of Empires, food and building materials have to be transported from their production points to a storage facility; during transport, these items can be stolen or destroyed by an enemy. Once stored, however, materials become intangible: They cannot be seized or destroyed even if the enemy demolishes the storage facility.
Similarly, most construction and management simulations and real-time strategy games don't require a resource to be physically transported before it can be spent or consumed; the commodity simply vanishes. When constructing a building in Age of Empires, the player doesn't transport the stone from the storage pit to the construction site. This takes an extra management burden off the player. The section "Logistics" in Chapter 14, "Strategy Games," discusses the gameplay implications of intangible resources at greater length.
