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StarCraft Portal: Resources
StarCraft is based on collecting two different Resources: Minerals and Vespene Gas. They differ through their gathering mechanic.
Minerals are used to construct buildings and units. Basic buildings, low-tech army units, and workers cost Minerals and not Vespene. A base normally has several Mineral patches. Workers assigned to gather Minerals return them to their Town Hall in packets of eight. An increase in mineral income can be achieved by improving the saturation of the Mineral Line by adding additional workers. When minerals are mined out, the patches vanish entirely. Read more about ideal mining.
Also known as just "gas", Vespene is used for higher-tech units and is especially important in late-game situations. There are no units that cost only gas. Vespene is collected from geysers upon which a race-specific structure (Assimilator, Refinery, Extractor) must be built. Workers assigned to the structure return Vespene packets to the Town Hall. Vespene is initially collected in quantities of eight. Once the main content of a Geyser has been depleted, workers will still collect gas indefinitely (unlike Minerals), but only in quantities of two. The sprite of gas carried by the worker decreases in size to indicate this.
Gas has a linear rate of gathering: the gas recovered from each geyser is constant since it is saturated with only a few workers. Professional maps yield maximum gas (about 288 gas per Fastest minute) with three workers per geyser, while other maps may need four or five. As a result of the constant rate of mining, improving your gas income usually requires additional bases.
Players begin in possession of one base and usually must create and defend additional bases, known as Expansions, throughout the game to secure more resources, whilst also attempting to stop enemy players from doing so. In StarCraft, map control is usually synonymous with resource control.
The production of almost every unit requires an additional resource: Supply. The amount of supply can be increased by the building of certain buildings or units. Supply is sometimes called Psi for the Protoss and Control for the Zerg. Another general term for Supply is Food.
Building either will increase the amount of supply each race is able to spend (the so-called Supply Cap), but it is economically inefficient to build Command Centers, Hatcheries, or Nexuses for supply, so these are generally not built for this purpose alone. The maximum amount of food for any player is 200.
It is worth noting that Supply, Control, and Psi, for Terran, Zerg, and Protoss respectively, are treated as separate resources in-game. By having control over each race, you can build 200 supply's worth of units for each race you control.
The term "Supply Block" or "being supply blocked" means that a player's current Supply Cap is no more than the Supply that his current units cost, e.g. "18/18", and he is thus unable to build any more. It may also mean that the Supply Cap is too low to build a certain unit. For example, a player at 38/41 cannot build a Reaver, which costs 4 Supply, so the Reaver may be described as supply-blocked, even though other units can be built.