Free Portal 2 DLC out October 4

Following the release of the well-received Portal 2 in April, Valve marketing director Doug Lombardi said the puzzle game would receive free downloadable content over the summer. However, summer has come and gone without further word on the DLC.

Valve ended its silence today, titling the complimentary DLC "Portal 2: Peer Review" and scheduling it to arrive simultaneously on the PC, Mac, Xbox 360, and PlayStation 3 next Tuesday, October 4.

The pack continues the cooperative adventures of P-Body and Atlas, who will ultimately take on GLaDOS in a new test track. The pack also includes a Challenge mode playable both in single-player and co-op, as well as leaderboard support.

Portal 2--which has shipped 2 million units--is the continuation of the 2007 Orange Box pack-in Portal. The single-player portion of the new title continues the travails of human lab rat Chell, who in the original game used a portal gun to create interdimensional openings on ceilings, walls, and floors in an effort to escape the Aperture Science labs and thwart the diabolical artificial intelligence known as GLaDOS.

For more on the title, check out GameSpot's review of Portal 2.