5.1 Surround Sound, HD (High Definition). Winner of over 30 ‘Game of the Year’ awards, ‘Portal’ now comes to the Xbox LIVE Arcade! As unwilling test subjects in a sinister laboratory, players must break the laws of physics using ‘portal’ technology to solve puzzles and survive. Unlock the full game to experience the complete singleplayer story, gain access to all 14 new bonus maps, and get a glimpse behind the scenes with developer commentary! This game requires the Xbox 360 hard drive. There are no refunds for this item. For more information, see www.xbox.com/live/accounts.