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 an exclusive DLC available to owners of the Razer Hydra. The DLC includes specific levels and mechanics that make use of the Hydra's motion detection functionality.

Peer Review
Peer Review is the first DLC released for Portal 2. Released on October 4th, 2011; this DLC introduces Challenge modes for both single-player and co-op, a leaderboards system, and a mini-hub area reserved for additional co-op tracks. This DLC adds the first of many additional courses to come with the introduction of the Art Therapy testing course.

Perpetual Testing Initiative
Perpetual Testing Initiative is a DLC released on May 8th, 2012; this DLC adds the anticipated in-game Puzzle Creator - fully integrated with the Steam Workshop, allowing the community to easily create, share, and play a wide range of Portal 2 puzzles.

It also allows you to play as a character that some people call "Bendy". A little black stick figure that appears in the trailers of Portal 2. This was so that the Perpetual Testing Initiative didn't interfere with the Portal 2 storyline by having Chell play them.

Portal 2 in schools
During a keynote presentation at the festival in 2011, Valve director Gabe Newell mentioned that the company was beginning to work with schools to build curricula around Portal 2, looking into "how to teach attraction, repulsion... [they] need to be clear on what their metrics are... what the outcome is, what they're optimizing for".