Portal 2 is the amazingly imersive and fun sequel to the amazingly imersive and fun videogame known as portal. It isn't however one of those sequels where they give you the same product with prettier graphics and do nothing to improve on it; the game contains many great new innovations. At its core, portal is a puzzle platformer game, and this aspect is combined with the story in a way that forces you to think of outside-the-box solutions. The characters are all compelling; even the silent protagonist gets some characterization during the game. She's smart, good at jumping, and is able to jump over both emotional and physical obstacles with ease. When things get tough, and she has a murderous AI tryng to kill her at every turn, she just keeps testing.
The game has essentially three modes. There's the story, co-op, and community made maps. The community for this game is amazing. They take all the resources Valve has lent them, and they make games barely recognizable as part of portal. It could also go in the opposite direction, and you get a game that feels like it should be a part of the main story. One major downside is that you cann't play co-op, or in community maps, if you lack an internet connection. There are many great maps that make you think and analyze the tools you're given in different ways; It's a shame that you can't just download and play one of them while on the go.
If you're not into puzzle platforming, in-depth and imersive storytelling doesn't impress you, and you don't like any of your friends enough to play this with them without committing murder, this isn't the game for you.