Beautiful soundtrack, landscapes, and story. A wonderful world to explore and take some time to look at when you aren't running around killing enemies.
What strikes me most is the level design; this game has a clear sense of progression and it is very easy to understand where you are supposed to be and where you are not. The puzzles are carefully thought-out and very unique, without being so alien that they are frustrating. As you gain more and more different abilities by progressing through the game and in some instances, exploring the world, the puzzles and movement challenges become more difficult but offer increasingly satisfying rewards.

Play with a controller, if possible. The movement in this game is incredibly fluid.