The game is a FPS, but differs from most others in that the player can choose the perspective to play from: Alien, Predator or Human (Colonial Marine). These different perspectives afford distinct capabilities and weapons. In the single player mode, the game presents a conventional series of levels to progress through. However, because of the differing abilities of the three species, the levels themselves are not always conventional in structure - Alien levels, for instance, often involve climbing through convoluted buildings. The levels are loosely structured, with progression sometimes a little arbitrary (e.g. Predator players find themselves, for a single level only, on the prison planet Fiorina 161 from the film Alien 3).
Human[edit]
In the most conventional case, playing as a human is the most similar to other FPS, and the player is able to access a wide array of weaponry (mostly that from the films). As well as powerful weaponry, Marines wear armour for protection and have an image intensifier and flares to improve visibility in dark environments.
Predator[edit]
As a Predator, the player may make use of Predator weapons such as the Plasmacaster, Smartdisc and Wristblades. Predators are also somewhat more athletic than humans, are the most durable creature in the game by far (even surpassing the armor capacity of armored humans in terms of withstanding damage), can make use of a cloaking device to stalk prey, and have a range of different vision modes to aid them in hunting the other species. In addition, they are capable of falling from far greater heights than humans without fear of injury or death. In the game, default Predator vision is similar to that of humans, but an infrared vision mode is available for tracking humans (similar to that in the Predator films), while a vision mode sensitive to electrical systems allows Predators to track Aliens (and androids).
Alien[edit]
Playing as an Alien is the most significantly different perspective. Players are able to range freely over any surface regardless of its inclination. This allows wall-walking and completely novel means of attack. However, weaponry is restricted to claws, tail and jaws (for the infamous head-bite), though these themselves reward the player with a fairly unusual experience in FPS combat. By default, Aliens visually perceive the environment in a similar manner to humans, albeit distorted by a fisheye lens to increase field of view. Players can also switch to a "sonic resonance" or echolocation mode to increase visibility in dark environments (as explained in Aliens versus Predator 2). This is augmented by an ability to detect pheromones and to discern human or Predator prey. The Aliens in this game can drop from any height without fear of injury or falling, and are the fastest of the three character species that the player can use.