Portal 2 picks up where Portal left off, preserving the same original concepts and attitude. This time, however, there are more portals, more physics, less portals, more flubber and other goos, and other new surprises. This game is longer and more story driven than the first.
The main attraction here is the puzzles, which at times require some creative thinking. If you have played Portal, you may find Portal 2 puzzles less challenging simply because you have practice. The good news is that there are some new mechanics added in to change things up, like the gels. Also worth noting is that there seems to be less emphasis on perfect portal placement in many puzzles, since valid portal surfaces are limited, and more emphasis on putting all the provided pieces together. Some good news for casual gamers is that there is also low reliance on quick reflexes.
The game also features a co-op mode, extending the game with puzzles requiring cooperation between two players to solve. This drastically increases replayability since you can get a new experience with a different partner. For example, you can find fun and creative new ways to kill your partner. This part is very well done, with gestures, signaling (such as a synchronized count-down), and voice chat. It also appears easily extendable, which might mean more content being added later.
Portal 2 is an amazing science-fiction comedy first-person puzzle action adventure game. The story is brilliant and absolutely hilarious, with lots of unexpected turns. Definitely recommended!