A 2D puzzle solving game, with the ability to shift time. While Prince of Persia: Sands of Time allowed you to shift time also, it was only for a limited amount of time, and wasn't used to solve puzzles. In this game, you use that ability to solve puzzles. Some of them are hard, but not impossible -- the thing is that they require unintuitive thinking -- you must use time shifting fully. It's really all you do, solve puzzles, and also follow the story.
The part I enjoyed most though was the graphics. Very nice painterly-style graphics, done by David Hellman.