Apogee Software was an American game publisher founded in 1987 that helped popularise the shareware model for PC games, releasing titles in episodes with the first part free. The company published and developed series including Commander Keen, Wolfenstein 3D and Duke Nukem, and its short intro fanfare played before many of those games began. As retro gaming grew online, recordings of the logo sting were shared as a standalone sound, kept alive by players who associate it with booting up a favourite DOS title.