KOPS is a two-dimensional gravitational cave flying game. The game is primarily designed to be multiplayer, but only local split screen game mode is provided. It is best played with 2-4 players on a single computer, but also a single player mode is available, which is suitable mostly for practicing. The original version was released back in 1996 as shareware software. After that the game has been released as a special slimmed down edition for the Disccover game competition. In 2001 the game was ported from DOS to Windows and released as freeware, and a few months later it was also ported to Linux. In 2003 the game has been released as open source, so it is publicly open for further development.