The game involves a lone Marine investigating a distress call from one of Mars' moons, which the player (controlling the Marine) must make their way through over a dozen levels, trying to stay alive while battling against a variety of creatures, ex-Marines, and various other dangers, such as traps that can cause damage, if not death to the player. There is also a multitude of weapons for the player to pick up and use, along with ammo and several ways to increase a player's health and armor status.