This is a first-person shooter in which players assume the role of a marine on a mission to stop a demonic invasion on Mars. Players use pistols, shotguns, rocket launchers, and chainsaws to kill mutant enemies and demonic creatures. Large blood-splatter effects occur frequently as enemies get decapitated and/or dismembered during combat; a handful of sequences depict mutilated corpses with exposed organs/viscera strewn in the environment. Some attacks result in finishing sequences that depict intense acts of violence: players using a chainsaw to slice open an enemy's head; players ripping the heart out of a creature and shoving it in its mouth; players sticking a gun in a creature's mouth and pulling the trigger. The words "f**k" and “sh*t” appear in the game.