At the start of a game of StarCraft, players choose one of three races, each with distinct unit abilities and gameplay approaches. Players’ actions are governed by the in-game economy; minerals and gas must be gathered in order to produce new buildings and units. The opposing player builds up their base at the same time, but each player can only see parts of the map within range of their own units. Thus, players must send units to scout unseen areas in order to gain information about their opponent, and then remember that information over a long period of time. This makes for an even more complex challenge as the environment becomes partially observable - an interesting contrast to perfect information games such as Chess or Go. And this is a real-time strategy game - both players are playing simultaneously, so every decision needs to be computed quickly and efficiently.