It was created by Tripwire Interactive for the ARG. These maps were included in the retail copy of Killing Floor when it was first released, with the achievements The Long War, The Hard War and The Completely Suicidal War awarded upon completing all five maps on Normal, Hard and Suicidal difficulty levels respectively (As of this time, there is no achievement for completing all five maps on Hell on Earth difficulty).Īperture is based off of the test chambers in the Aperture Science test facility.