Though short on details, Valve hasn't wasted any time confirming its plans for Portal 2 DLC. After a massive launch just over a week ago – Valve says Portal 2 is its "fastest-selling" release since Half-Life 2! – the famously generous developer has outlined what it's calling "Portal 2 DLC #1."

For the asking price of $0, DLC #1 will offer "new test chambers for players, leaderboards, challenge mode for single and multiplayer modes, and more." While free DLC on the Steam-powered PC and Mac platforms is nothing unusual coming from Valve, DLC #1 will notably be "free of charge" on Xbox 360 and PS3 as well. Of course, adding Steam to the PlayStation 3 release was always intended to allow for this scenario, and we can only imagine Microsoft didn't feel comfortable with the Xbox 360 being the sole platform charging for otherwise free content.

Portal 2 DLC #1 is "targeted" for release this summer; it's not clear if that estimate is Normal Time or Valve Time, so don't mark up your Stephen Merchant calendars just yet.
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April 29, 2011 - Valve, creators of best-selling game franchises (such as Half-Life, Left 4 Dead, Team Fortress, and Counter-Strike) and leading technologies (such as Steam and Source), today announced the first game add-on for the year's highest rated multiplatform game, Portal 2, is in development and targeted for this summer.

Portal 2 DLC #1 will offer new test chambers for players, leaderboards, challenge mode for single and multiplayer modes, and more.

Targeted for release this summer, Portal 2 DLC #1 will be offered free of charge for the PC, Mac, Xbox 360, and PS3.

Portal 2 was released April 19 and currently holds a Metacritic score of 95%, making it the top rated multiplatform game of 2011. Portal also captured the number 1 chart position in the UK, Germany, and the Nordic countries during its first week of availability, making it the fastest-selling Valve release since Half-Life 2.

A hilariously mind-bending adventure that challenges you to use wits over weaponry in a funhouse of diabolical science, Portal 2 features expansive single and cooperative multiplayer game modes.

For more information, please visit www.thinkwithportals.com

This article was originally published on Joystiq.