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 second game add-on for the year's highest rated multiplatform game, Portal 2, is in development and targeted for release early next year.

This major update will feature an easy-to-use in-game map editor that will let users design, build and share their own single-player and co-op test chambers with the community, who will be able to view, play and vote on them with a simple click.

Portal 2 was released April 19, and currently holds a Metacritic score of 95%, making it the top-rated multiplatform game of 2011. Its first content update, "Peer Review", came out two weeks ago.

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 on Portal 2 and its downloadable content, please visit http://www.thinkwithportals.com.

That's pretty damn cool. In game editing makes it accessible to everyone. Would be neater if it allowed you to build with a friend.