Portal

Portal is a first-person puzzle game developed by Valve Corporation and released in late 2007, first as part of The Orange Box for Windows, Steam, Xbox 360 and the PlayStation 3, and later as a standalone title for Windows and Steam. In the game, the player controls a female test subject named Chell in the Aperture Science Enrichment Centre. Guided by a female electronic voice-over of a supercomputer named GLaDOS, the player uses the Aperture Science Handheld Portal Device ("portal gun") to perform a variety of tests, such as creating portals to knock over turrets and other objects or moving to a previously unreachable area, so that they may advance to the next test.

Portal is set in the Half-Life universe, and although there are no direct references to it in the game, there are many similarities between equipment in Portal and in Half-Life 2; turrets, for example, are quite similar in both games, and Portal also uses energy orbs identical to those in Half-Life 2. The backstory to Portal is explained in Half-Life 2: Episode Two, although the story behind the protagonist is explained throughout Portal.

Portal is the sequel to Narbacular Drop, a freeware game released by students of the DigiPen Institute of Technology, and also ties in with the Half-Life series through Half-Life 2: Episode Two, with a full conclusion expected in Half-Life 2: Episode Three.

Story
You awake as Chell, a woman equipped with implanted heel springs to help her fall from great heights, in the middle of a relaxation room. Immediately the mechanical voice of GLaDOS greets you. It's time to be tested as a human lab rat. Will the experiments go as planned? Just remember: the cake is a lie.