Killing Floor (Year 2009)

Killing Floor is a cooperative first-person shooter video game developed and published by Tripwire Interactive. It was originally released as an Unreal Tournament 2004 mod in 2005. Retail release followed on May 14, 2009, for Microsoft Windows, and for OS X on May 5, 2010. The Linux version was released on the Steam platform in November 2012. A sequel was announced on May 8, 2014.