Pretty fun! The destruction mechanics are really interesting, and it follows the theme pretty well. However ,I felt the pickaxe invalidated the other tools, as it was suffiicient to get all keys. Maybe that changes on later levels though.
The graphics aren't bad, but there is a inconsistency of styles between the gate, with it's gradient shadows, the terrain, which isn't shaded at all and the fog in the backgroud that is too detailed.
The music was mysterious and fit the atmosphere, but is really repetitive.
Overall it's a nice game, unfortunately I couldn't figure out how to get past the second level, I got stuck on how to return to the gate after getting the keys to the left. The only thing that I really didn't like is how you need to make "leaps of faith" some times to get to certain platforms. In my opinion, it's very important to always know where you're jumping at in a platformer.