Aliens: Colonial Marines is a first-person shooter based on the Alien science fiction horror film series. The game's campaign mode, which can be played by a single player or cooperatively by up to four players, features 11 missions that involve players moving from one checkpoint to another while fighting opponents controlled by the game's artificial intelligence. Opponents consist of either Alien creatures, also known as Xenomorphs, or hostile human mercenaries. Xenomorphs are fast and primarily attack with their claws or by spitting acid, while mercenaries are slower and use firearms.
As the fictional Colonial Marines military unit depicted in James Cameron's 1986 film Aliens, players have access to weapons such as pistols, shotguns, grenades, pulse rifles, flamethrowers, robotic sentry turrets, and smartguns, which automatically track and target opponents. They may also use welding torches to seal doors and motion trackers to detect unseen enemies. Ammunition can be found on defeated mercenaries or from certain locations in the mission area. The Colonial Marines are protected by a health bar that is divided into segments. If a segment is partially depleted, it will automatically regenerate over time. Med-Packs throughout the missions may be acquired to restore lost health segments. Players may also collect pieces of armor that protect the health bar with a secondary meter that does not automatically regenerate. Players have a limited time to revive a player whose health has been fully depleted. If they fail to do so, the downed player cannot return to the game until the surviving players reach the next checkpoint.
In addition to the campaign mode, Colonial Marines features a competitive multiplayer mode where two teams of up to five players face each other in four different scenarios. Each scenario involves one team playing as Colonial Marines and the other as Aliens. After a time limit has been reached, players switch roles and play once more on the same map. Scenarios include Team Deathmatch, where both teams must kill as many opposing players as possible; Extermination, where Colonial Marines must detonate bombs in egg-infested areas protected by Aliens; Escape, which involves Colonial Marines completing objectives to reach a destination while being assaulted by Aliens; and Survivor, where Colonial Marines must survive attacks from Aliens with limited health and ammunition resources for as long as possible. Unlike Colonial Marines, Alien players play from a third-person perspective and cannot use firearms, but have the ability to climb walls, run on ceilings, deliver attacks with their claws, and unleash streams of acid.
Players earn experience points by overcoming opponents, completing challenges, and finding collectibles—Audio Logs, Dog Tags, and Legendary Weapons, all of which related to characters who appear in the film series. Challenges range from killing opponents in a particular way to winning multiplayer matches and completing campaign missions under a difficulty setting. Players have two ranks, one for their Colonial Marine character and another for their Alien character. When a sufficient amount of experience has been obtained, their characters rank up. Colonial Marine ranks unlock weapon upgrades for use in both the campaign and the competitive multiplayer modes. These include alternate fire attachments, telescopic sights, and larger capacity magazines. In contrast, Alien ranks unlock new combat abilities for Alien characters. Completing challenges also unlock appearance options for both Colonial Marine and Alien characters, and new attributes that are exclusive to Colonial Marines in the competitive multiplayer mode.
Plot
17 weeks after the events of Aliens, the Sephora spaceship sends a full battalion of Colonial Marines to investigate the Sulaco spaceship, now in orbit around the LV-426 moon. A massive Xenomorph infestation is discovered inside the Sulaco and several Marines are killed in the initial onslaught. Corporal Christopher Winter, private Peter O'Neal and private Bella Clarison discover that hostile mercenaries working for the Weyland-Yutani corporation are in command of the Sulaco and have been breeding Xenomorphs on board for study. Shortly before both ships are destroyed in the ensuing confrontation, the Marines, along with commander Captain Cruz, Sephora android Bishop and pilot lieutenant Lisa Reid, escape aboard her dropship and take shelter in the ruins of the Hadley's Hope colony complex on LV-426.
Although the Marines learn that Clarison has been attacked by a facehugger and needs medical treatment, Cruz orders Winter to travel to a nearby Weyland-Yutani research facility set up near a derelict Xenomorph spacecraft and recover a manifest that identifies an unknown prisoner from the Sulaco. In an attempt at saving Clarison, Winter and O'Neal accept the mission and escort her to the facility, where they intend to convince surviving personnel to remove the Xenomorph embryo from her body. However, upon arrival, an interrogated Weyland-Yutani medical officer explains to them that Clarison's life cannot be saved because the creature's invasive placenta is cancerous and will eventually kill her even if the embryo is successfully extracted. Clarison dies shortly after a chestburster hatches from her.
