The game consists of four levels. The first level begins with United States Colonial Marines storming a Human colony on LV-426. After clearing the inside, outside the human defenses are corrupted and begin to attack the humans. Making it back inside, human android Synthetics attack. Soon, the players are forced to attack a robot-like power-loader piloted by an android. Continuing, the player(s) are picked up by an APC and taken deeper into the hive. Androids and Sentry Guns attack the player(s) in greater numbers. Soon, the gamer(s) end up inside of a hive, and using infra-red vision for a short time, fight off aliens. Before long, they face an Alien Dragon, or a winged alien and winged chestbursters. Deeper into the hive, they fight off the Queen of the hive and defeat the game.
Shooting is done with plastic model M41A Pulse Rifles. Each rifle has a trigger, a button to fire a grenade near the end of the barrel, and a button under the hand guard to fire a napalm-fueled flamethrower. Though the Pulse Rifle can do both fully automatic and bursts of four shots in other media, in the game the M41A can only fire at a fully automatic setting.