Halo: Combat Evolved is a first-person shootervideo game developed by Bungie and published by Microsoft Game Studios. The first game of the Halo Series, it was released on November 15, 2001 as a launch title for the Xbox gaming system and is considered the platform's "Killer apps" With more than five million copies sold worldwide as of November 9, 2005, Microsoft released versions of the game for Microsoft Gaming and Mac OS X in 2003, and the surrounding storyline was adapted and elaborated into a series of novels and comic books. The game was later released as an Xbox Original for download onto an Xbox 360 HDD.
In Halo's twenty-sixth century setting, the player assumes the role of the Master Chief, a Cybernetically enhanced super-soldier. The player is accompanied by Cortana, an Artificial intelligence who occupies the Master Chief's neural interface. Players battle various aliens on foot and in vehicles as they attempt to uncover the secrets of the eponymus Halo, a ring-shaped artificial planet. The game has been called "easy to learn", and has been praised for its "engaging story".