Portal 2

Portal 2 is the sequel to the award winning and hugely successful Portal developed by Valve Corporation. It features a single-player story set after the events of Portal's story; and a brand-new Co-op game mode, featuring additional test chambers designed specifically for Co-operative play. Portal 2 was released April 19, 2011 on the Steam platform. North America got retail release on the April 19, 2011; Europe and Australia, April 21, 2011.

Sixense
The Portal 2 Sixense MotionPack DLC  is exclusive Portal 2 downloadable content available to owners of the Razer Hydra (Purchasable on the Steam store). The DLC includes specific levels and mechanics that make use of the Razer Hydra's motion detection capabilities.

Summer DLC (Unreleased)
Portal 2 is set to receive a free DLC in summer 2011. The DLC will include more levels for both single-player and co-op. The DLC will also add a new gamemode called "Challenge Mode". The Challenge Mode will most likely be something like the challenge mode seen in the original Portal.

Portal 2 in Schools
During Gabe Newell's keynote at the Games For Change festival, Gabe mentioned that Valve were beginning working with schools to build curricula around Portal 2; looking into, as Stephen Totilo of Kotaku summarised, "how to teach attraction, repulsion... they need to be clear on what their metrics are... what the outcome is, what they're optimizing for".

Trivia

 * Shooting a portal to the moon as the ending was originally an easter egg "3 minutes into the game", which caused the player to be sucked out of the test chamber and die - and was an alternate game ending.