Kaos is a first-person shooter. It was being developed by The Millennium group from Italy in 1995 and planned to be released as a sharware game. However, the game got cancelled. 2003 or 2004 the developers released the unifinished game together with the source code as freeware. The release version comes with three levels and an editor.

Kaos is a classic FPS very similar to Wolfenstein 3D, Doom and Rise of the Triad. While the levels still have a rectangular architecture like Wolfenstein, floors and ceiling are textured and you can look up and down.
A unique feature of the game is a multiplayer mode where up to three players can partake in spilt screen mode at the same computer.