The original StarCraft, its Brood War expansion, and StarCraft 2 Wings of Liberty are free to download and play from Blizzard's website. StarCraft II Heart of the Swarm expansion, which was released in March 2013, is a remastered version of the original StarCraft.
See also: StarCraft II: Wings of Liberty, StarCraft II, StarCraft (video game), Races of StarCraft, Characters of StarCraft, StarCraft: Brood War,