StarCraft Gameplay
During a game, the player must use units to gather minerals and vespene gas. They must also build structures or units which provide 'supplies'. Each type of unit costs a certain amount of gas, minerals, and supplies. If the player does not have enough of a resource, he or she cannot build more units. Resources are gathered by worker units. Minerals are needed for all units and buildings, and come as blue crystals from the ground. Vespene gas is needed for stronger units and comes as a geyser with green smoke blowing out of it. A special building must be built on these geysers before worker units can gather the gas.