Portal is a 2007 single-player first-person puzzle-platform video game developed by Valve Corporation. The game was released in a bundle package called The Orange Box for Microsoft Windows and Xbox 360 on October 9, 2007, and for the PlayStation 3 on December 11, 2007. The Windows version of the game is available for download separately through Valve's content delivery system Steam and was released as a standalone retail product on April 9, 2008. A standalone version called Portal: Still Alive was released on the Xbox Live Arcade service on October 22, 2008; this version includes an additional 14 puzzles. A Mac OS X version was released as part of the Mac-compatible Steam platform on May 12, 2010. The game primarily comprises a series of puzzles that must be solved by teleporting the player's character and simple objects using "the handheld portal device", a device that can create inter-spatial portals between two flat planes.
Contributions by Tom Edwards, Gamer007, and Enfestid.