The game was released on for the PC and on for the Mac OS X. It is a stand-alone version of the original total conversion mod for Unreal Tournament 2004, officially announced on March 2009, and was built on a heavily modified version of the Unreal Engine 2.5 owned by Epic Games. Killing Floor (also known as KF) is a first-person shooter video game developed and published by Tripwire Interactive for the PC and Mac OS X.