Portal 2

Portal 2 is a first-person puzzle-platform video game developed and published by Valve Corporation. The sequel to the 2007 video game Portal, it was announced on March 5, 2010, following a week-long alternate reality game based on new patches to the original game. Though initially slated for release in the fourth quarter of 2010, the game was postponed to the week of April 18, 2011. The game was released by Valve through Steam for Microsoft Windows and Mac OS X, while the PlayStation 3, Xbox 360, and retail Windows/OS X versions of the game are distributed by Electronic Arts. The game’s release on Steam was preceded by a second multi-week alternate reality game, the Potato Sack, involving 13 independently-developed titles which culminated in a distributed computing spoof to release Portal 2 several hours early.
Like Portal, Portal 2 primarily comprises a series of puzzles that must be solved by teleporting the player’s character and simple objects using the “portal gun”, a device that can create inter-spatial portals between two flat planes. The game’s physics allow momentum to be retained through these portals, which must be used creatively to maneuver through the game’s challenges. Most gameplay elements of the original Portal were retained in the sequel, and more were added to Portal 2, including tractor beams, laser redirection, and paint-like gels that impart special properties to objects they cover. These gels were created by the team from the Independent Games Festival-winning DigiPen student project Tag: The Power of Paint.