 "Portal" consists primarily of a series of puzzles that must be solved by teleporting the player's character and simple objects using "the Aperture Science Handheld Portal Device", a device that can create inter-spatial portals between two flat planes.The player-character, Chell, is challenged and taunted by an artificial intelligence named GLaDOS (Genetic Lifeform and Disk Operating System) to complete each puzzle in the Aperture Science Enrichment Center using the portal gun with the promise of receiving cake when all the puzzles are completed.The game's unique physics allows kinetic energy to be retained through portals, requiring creative use of portals to maneuver through the test chambers.