Portal, an innovative video game released in October 2007, is now available as a free download from Steam until May 24th.
Portal is a first-person shooter puzzle game that tests your problem solving abilities unlike any other game. The object is to use your portal gun to create portals that will teleport your character and other in-game objects across great distances and through treacherous terrain.
To find out more about Portal and see the game in action, watch this trailer from Steam.
Portal is available for free on Windows and as of May 15th, Mac as well. A free Steam account is required to play.