Electronic Arts Portal 2

The single-player portion of Portal 2 introduces a cast of dynamic characters, a host of fresh puzzle elements, and a much larger set of devious test chambers. Players will explore never-before-seen areas of the Aperture Science Labs and be reunited with GLaDOS, the occasionally murderous computer companion who guided them through the original game. The game's two-player cooperative mode features its own entirely separate campaign with a unique story, test chambers, and two player characters. This mode forces players to reconsider everything they thought they knew about portals. Success will require them to not just act cooperatively, but to think cooperatively.