Ascend over and across the cliffs of Phobos to shutdown "The Machine" and stop the UAC from opening the dimensional doors to Hell once again...
Just drag the Cliffs.wad file over the Doom application (tested with GZdoom 3.1) and fire up Episode 1 "Cliffs of Phobos" (It's only one map though).
This is my second Doom level and really proud how it turned out. :)