Nice puzzle game, good graphics and music.
Looping monster noises got a bit on my nerves after a while, especially when missing timing with the boulders, which can get really frustrating. The "thief" level particularly, one missed timing to get the monster to open the path to the door and you have to redo the entire level, waiting on the monsters to get into the right spot again.
I like that the first few levels teaches you the mechanics without holding your hand, and it becomes a bit more obscure after a while, which is good for the difficulty.
I'm not a super fan of puzzle game to begin with, so don't take it to heart, it might be just me being a dumb.