Killing Floor, a new zombie action game from Tripwire Interactive - makers of Red Orchestra, is now available for pre-order via Steam. Featuring multiplayer co-op action for up to six players, Killing Floor is now available for 25% off its regular price for those who pre-purchase the game before it is made available for play on May 14. Killing Floor features over 40 Steam Achievements, persistent perks to level up your character and a solo game mode for offline play.