6.370 Home: Background: Primer: Buildings & Tech Tree

A building is a specialised unit that is usually large and stationary, although in the implementation of traditional RTS games, buildings and units are treated as quite separate concepts. In many games, the destruction of all your buildings is sufficient for your defeat. The functions of buildings usually include the production of new units or the enabling of certain unit abilities. However, in StarCraft at least, some buildings can move (e.g. most Terran buildings) and some mobile units can produce other mobile units (e.g. carriers produce interceptors, reavers produce scarabs).

Nexus before any other building.		The Robotics Facility produces Reavers.		The Fleet Beacon enables you to build Carriers.

The technology tree, or tech tree, is the set of dependencies between buildings and between buildings and units. An example of the first kind is the fact that you must build a Nexus before you can build any other building, as shown in the diagram below. An example of the second kind is the fact that you must have a Cybernetics Core before you can train dragoons (this is not shown in the diagram). Note that these dependencies are just another kind of constraint, and represent the "build" part of our RTS model.

Partial tech tree for the Protoss