Portal 2 will allow cross-play between 4 platforms

Portal 2
Release Date: Apr 19, 2011
Official Website: Link
Crossplay platforms:
Portal 2 will support cross-play across multiple platforms. It will be possible to play together with your friends on Windows PC, Playstation 3, Linux and Mac. Please check out all the details on the game's official website!
Summary:
Sequel to the acclaimed Portal (2007), Portal 2 pits the protagonist of the original game, Chell, and her new robot friend, Wheatley, against more puzzles conceived by GLaDOS, an A.I. with the sole purpose of testing the Portal Gun's mechanics and taking revenge on Chell for the events of Portal. As a result of several interactions and revelations, Chell once again pushes to escape Aperture Science Labs.
You lost your memory, you are alone in a world full of danger, and your mission is survive using your mind. The only way to get out from this hell is.....Hi i'm GLAdOS, and welcome to the amazing world of portal 2, here i will expose you to a lot of tests, and try to k.. help Aperture Science envolve in a new era. Your job is advance in the levels i propose and get better and better, you will have an portal gun to help you, and remember nothing is impossible if you try, and try again and again and again.... The puzzles are waiting for you!

Screenshots:
Supported game modes:
  • Single player
  • Multiplayer
  • Co-operative
  • Split screen
Supported player perspectives:
  • First person