Prey is a first-person shooter, using a heavily modified version of the Doom 3 engine. The game’s engine introduces two unique aspects to exploration. Portals in the game can transport the player from one area to another instantly; portals can be looked and shot through as well (introducing the very real hazard of shooting oneself by mistake), and can also be traveled in reverse. The game also features variable gravity. Special paths allow the player to walk along them, remaining upright regardless of orientation, though should the player fall or voluntarily jump off the path, gravity will reassert itself.