Aliens: Colonial Marines is a first person shooter which puts the player in the role of a United States Colonial Marine named Cpl. Christopher Winter. The player has access to iconic weapons from the movie such as the flamethrower, pulse rifle, smartgun, shotgun, pistol, RPGs, and robotic sentry turrets. Players are also able to use welding torches to seal doors and motion trackers to detect unseen enemies.
Initially it was announced that the game would involve squad-based gameplay, allowing the player to issue orders to-controlled marines using context-sensitive commands. However, Gearbox later revealed that this feature was dropped to make gameplay more accessible. Aliens: Colonial Marines was originally planned to have no HUD to provide the player with onscreen information.
Gameplay types have been described as "Gauntlet Runs", where players must fight enemies as they travel from point A to point B, and "Last Stand" moments, where players must defend a specific area by welding doors and/or setting up automated sentry turrets.
The players gain experience points when killing enemies and completing certain objectives. These experience points allow players to customize the appearance of their character, purchase upgrades for weapons, and unlock other skill sets, all of which carry over to other gameplay modes
The primary enemies of the game are the from the first three films, which include the , and "Drone" alien from , the "Warrior" and the "Queen" aliens from , as well as the "Runner" alien from The "Crusher" alien is an original enemy, which was revealed in the E3 2011 Walkthrough demo. Another original enemy, the "Boiler" alien, is a variant capable of self-exploding and covering its enemies with molecular acid. It was revealed in the tactical multiplayer trailer.Along with being able to traverse different surfaces from any angle, the aliens' uses the environment to set up sneak attacks, and group tactics to overwhelm the player.Not all enemies are aliens, as players also find themselves fighting human enemies in the form of Weyland-Yutani commandos and mercenaries.