While most 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 goal of both campaigns is to explore the Aperture Science Laboratory-a complicated, malleable mechanized maze. When Chell dies in the single-player game, the game restarts from a recent checkpoint in the cooperative game, the robot respawns shortly afterwards without restarting the puzzle. There is no penalty for falling onto a solid surface, but falling into bottomless pits or toxic pools kills the player character immediately. Characters can withstand limited damage but will die after sustained injury. These three characters can explore and interact with the environment. 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. Portal 2 is a first-person perspective puzzle game. In this example, the vertical velocity of the falling character is converted into horizontal velocity by the portal. The player's speed does not change upon passing through portals. Portal 2 challenges the player to use teleportation to traverse obstacle courses. Like its predecessor, it has been described as one of the greatest video games ever made by numerous publications and critics. Portal 2 received critical acclaim for its gameplay, balanced learning curve, pacing, dark humor, writing, and acting. After release, Valve released downloadable content and a simplified map editor to allow players to create and share levels. Valve announced Portal 2 in March 2010, and promoted it with alternate reality games including the Potato Sack, a collaboration with several independent game developers. Jonathan Coulton and the National produced songs for the game.

In the new cooperative mode, players solve puzzles together as robots Atlas and P-Body (both voiced by Dee Bradley Baker).

In the single-player campaign, players control Chell, who navigates the dilapidated Aperture Science Enrichment Center during its reconstruction by the supercomputer GLaDOS ( Ellen McLain) new characters include robot Wheatley ( Stephen Merchant) and Aperture founder Cave Johnson ( J. Portal 2 adds features including tractor beams, lasers, light bridges, and paint-like gels that alter player movement or allow portals to be placed on any surface. Like the original Portal (2007), players solve puzzles by placing portals and teleporting between them. The digital PC version is distributed online by Valve's Steam service, while all retail editions were distributed by Electronic Arts. Portal 2 is a 2011 puzzle-platform video game developed by Valve for Windows, Mac OS X, Linux, PlayStation 3, and Xbox 360.

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