Portal is a single-player first-person action/puzzle video game developed by Valve. The game was released in a bundle package known as The Orange Box for PC and Xbox 360 on October 10, 2007, and will be released for the PlayStation 3 sometime in November. The Windows version of the game is also available for download separately through Steam.[2] The game consists of a series of puzzles which must be solved by teleporting the player's character and other simple objects using the Aperture Science Handheld Portal Device. The goal of each puzzle is to reach an exit point. The "portal gun" and the unusual physics it creates are the emphasis of this game.

n Portal, players control Chell (as she is named in the game credits), a test subject in the Aperture Science Enrichment Center. Gameplay revolves around the "Aperture Science Handheld Portal Device" (also known as the "portal gun"), a handheld device that can create an intra-dimensional portal between flat planes, allowing instant travel and a visual and physical connection between any two different locations in 3D space. Portal ends are restricted to planar surfaces, but if the portal ends are on different planes, bizarre twists in geometry and gravity can occur, such as the player walking into the portal through a wall and "falling" up out of the floor several feet behind where she started. An important aspect is that objects retain their momentum as they pass through the portals