This is a first-person shooter in which players assume the role of a soldier who must help defend humanity against an alien invasion. Players use handguns, machine guns, sniper rifles, and rocket launchers to kill aliens and other human soldiers in frenetic combat. Battles are highlighted by realistic gunfire, screams of pain, and large explosions. During the course of the game, players are able to use stealth attacks to break enemies' necks or slice their throats. Injured characters generally emit large splashes of blood from their chests and necks, and some levels depict large bloodstains on the floor or walls. In one sequence, players' character encounters cages filled with human corpses (some with exposed buttocks). The words "f**k" and "sh*t" can be heard in the dialogue.