Portal 2 is a first-person perspective puzzle game. The player takes the role of Chell in the single-player campaign, as one of two robots—Atlas and P-Body—in the cooperative campaign, or as a simplistic humanoid icon in community-developed puzzles. Characters can withstand limited damage but will die after sustained injury.[2][3] The goal of both campaigns is to explore the Aperture Science Laboratory—a complicated, malleable mechanized maze. While some parts of the game takes place in modular test chambers with clearly defined entrances and exits, other parts occur in behind-the-scenes areas where the objective is less clear.
The initial tutorials guide the player through movement controls and interactions with their environment, and in the case of the cooperative campaign, interactions with the other player. Gameplay revolves around the use of the Aperture Science Handheld Portal Device, which can create a pair of two portals on suitable surfaces through which the player or objects can pass through. Characters can use these portals to move between rooms or to "fling" objects or themselves across a distance.[4][5]
Additional game elements not featured in the original Portal include Thermal Discouragement Beams (lasers), Excursion Funnels (tractor beams), and Hard Light Bridges, all of which can be transmitted through portals.[2][6][7][8] Aerial Faith Plates catapult the player and objects through the air. The player must disable sentient, lethal turrets or avoid their line of sight. The Weighted Storage Cube has been redesigned, and there are new types: Redirection Cubes, which have prismatic lenses that redirect laser beams, spherical Edgeless Safety Cubes, an antique version of the Weighted Storage Cube used in the underground levels, and a cube-turret hybrid created by Wheatley after taking control of Aperture.[2][9] The heart-decorated Weighted Companion Cube reappears briefly.[10] Early demonstrations included Pneumatic Diversity Vents, shown to transport objects and transfer suction power through portals, but these do not appear in the final game.[2][9][11][12] The typical objective of a test chamber or level is to use the portal gun and provided gameplay elements to open a locked exit door and progress to the next chamber.
