Portal 2 is a game sequel to the award-winning game, Portal. Featuring an innovative single-player puzzle game, with new and fresh puzzle elements as well as a much bigger set of devious test chambers. Everything you though you know from the previous game will be debunked in this game. Act competitively, but think cooperatively,  

• SINGLE PLAYER MODE: Featuring next-generation gameplay and a wildly engrossing story.
• TWO-PERSON MULTIPLAYER MODE: A new mode adding a whole new twist to the game with a different campaign from the single-player mode
• Advanced physics: This allows for the creation of a whole new range of interesting challenges, producing a much larger but not harder game.
• Editing Tools: Portal 2 editing tools will be included.

Reviews

Sporting some of the best writing and voice work in years (as well as some deviously designed puzzles), Portal 2’s single-player campaign is superior to its predecessor in every way. It’s the co-op mode, however, that makes this 2011’s first must-play game — even for those gamers that don’t like first-person or puzzle games.

GameSpy    

Portal is perfect. Portal 2 is not. It’s something better than that. It’s human: hot-blooded, silly, poignant, irreverent, base, ingenious and loving. It’s never less than a pure video game, but it’s often more, and it will no doubt stand as one of the best entertainments in any medium at the end of this year. It’s a masterpiece.

Eurogamer