StarCraft focuses around three distinct interstellar species: the psionic Protoss, the adaptable Terrans, and the insectoid Zerg.
The game revolves around players collecting resources to construct a
base, upgrade their militaries, and ultimately conquer opponents. Brood War's gameplay remains fundamentally unchanged from that of StarCraft, although it introduces fine-tuning to unit costs and some abilities for strategic and balance purposes. These changes make rushing tactics—a factor that gained some criticism in the original StarCraft—less practical.
The single-player campaign has an increased difficulty; missions are no
longer entirely linear, and a greater focus on strategy is needed to
complete missions. In addition, the game's artificial intelligence (AI) has been augmented so that AI-controlled players are more intelligent and tends to use tactics more effectively.
Brood War introduces seven new units. Each race is given
access to a unique ground unit: the Zerg can create a defensive unit
that can attack from the concealment of its burrow, while the Terrans can train combat medics. The Protoss are able to produce dark templar units, a powerful cloaked melee unit only given to the player in special missions of StarCraft. Protoss players can merge two of these units to create a special spellcaster unit. Each race is also given access to a dedicated air-to-air attack unit.