Halo: Combat Evolved was released in 2001. Bungie developed the science-fiction first-person shooter, and Microsoft Game Studios published it as an Xbox launch title in North America on November 15, 2001.
The game began as a project for Macintosh computers before Microsoft acquired Bungie and repositioned it as a flagship Xbox title. Its campaign introduced Master Chief, Cortana, the Covenant, the Flood, and the mysterious ringworld later known as Installation 04.
The subtitle “Combat Evolved” distinguished the game from earlier working titles and emphasized its attempt to expand the console shooter formula. It is sometimes informally called Halo 1, but its official title is Halo: Combat Evolved. The PC version followed in 2003, while Halo: Anniversary later recreated its campaign for modern platforms.