Portal 2 is a 2011
first-person puzzle-platform video game developed and published by
Valve Corporation. It is the sequel to
Portal (2007) and was released on April 19, 2011, for
Microsoft Windows,
OS X,
Linux,
PlayStation 3, and
Xbox 360. The retail versions of the game are distributed by
Electronic Arts while online distribution of the Windows, OS X and Linux versions is handled by Valve's content delivery service
Steam.
Portal 2 was announced on March 5, 2010, following a week-long
alternate reality game based on new
patches to the original game. Before the game's release on Steam, the company released the
Potato Sack, a second multi-week alternate reality game, involving 13 independently developed titles which culminated in a
distributed computing spoof to release
Portal 2 several hours early.