It's a cross between a sliding tile puzzle and a platform game. If you've been a long-term sufferer of mediocre-to-crap adventure games, the words "sliding tile puzzle" should drive a spike made of terror directly into your heart, but fear not, it's not that way at all. Instead you must find variant ways the small scenes can be perfectly aligned (from one of four sides) to others, thus allowing your little stick man to move from one to the next. In pursuit of keys.
My only criticism here is the time it takes to get going. The concept isn't perhaps quite as complex as the learning curve might think it is. I found myself anticipating challenges before the game thought I was ready. However, get deep enough in and all those clever new ideas begin to appear. Figuring out a new method to reach a tile is very satisfying. It's also extremely well designed, zooming in and out from tile puzzle to platform game elegantly with a hit of Space, minimal controls effectively deployed.