Portal

Portal is a story-driven puzzle game, developed by Valve and released as part of The Orange Box and stand-alone for Microsoft Windows, Mac OS X, Xbox 360, and PlayStation 3.

In Portal, the player is challenged by an artificial intelligence, GLaDOS (Genetic Lifeform and Disk Operating System), to complete a series of puzzle rooms in the Aperture Science Enrichment Center testing laboratories, with the promise of receiving cake when all of the puzzles have been completed. Puzzles revolve around the use of a Aperture Science Handheld Portal Device, or Portal gun, which can create inter-spatial portals between two flat planes; a gameplay concept first utilised in the game Nerbacular Drop.