Return to Aperture Laboratories in Portal 2 where you’ll once again face off with the lethally inventive, power-mad A.I. named GLaDOS. Meet an expanded cast of characters as you think your way through dangerous, never-before-seen areas of the laboratories and a wider variety of portal puzzles. Plus Portal 2 also includes a co-operative game mode with local, split-screen and online multiplayer so you and a friend can think with portals.

More details on the official game page of Portal 2 ...