This is a third-person shooter in which players assume the role of an elite space marine whose unit is tasked with combating an alien invasion. Players use machine guns, axes, explosives, and chainsaw-swords to kill hordes of enemies (e.g., demons, goblin-like creatures, human agents) during frenetic gunfights and melee-style combat. Battles are highlighted by slow-motion effects, screams of pain, and exaggerated splashes of blood that stain the ground and players' bodies; enemies collapse to the ground or break into bloody fragments when killed. Some weapons can decapitate/dismember enemies, while others may briefly become lodged in creatures' bodies. Players can also stomp on felled enemies' heads to complete a kill, resulting in decapitation and additional blood effects.