The sound design is really good and it complements the game so well! I love how tension builds up every time the monster moves (cue dramatic chord). It really adds to the sense of urgency and that sort of thing is perfect for this kind of game. The last few levels are pretty difficult and it took me a few tries, but I managed to clear all 20 levels.
The game's simplicity works greatly in its favor in my opinion because it makes the monster that much more threatening. Great work!