Doom (stylized as DOOM) is an American media franchise created by John Carmack, John Romero, Adrian Carmack, Kevin Cloud, and Tom Hall.[1] The series usually focuses on the exploits of an unnamed space marine (often referred to as Doomguy or Doom Slayer) operating under the auspices of the Union Aerospace Corporation (UAC), who fights hordes of demons and the undead to save Earth from an apocalyptic invasion. The original Doom is considered one of the first pioneering first-person shooter games, introducing to IBM-compatible computers features such as 3D graphics, third-dimension spatiality, networked multiplayer gameplay, and support for player-created modifications with the Doom WAD format. Over 10 million copies of games in the Doom series have been sold; the series has spawned numerous sequels, novels, comic books, board games, and film adaptations.