Character art is superb! Lots of neat little animation touches, and the audio and lighting made for a really good atmosphere. Mechanics suited both the theme and constraint, and the level design is well paced, if a little unforgiving.
It would be good to communicate the power-ups a little better, it took me a while to understand that they wore off, and I had some difficulty jumping away from slopes, but it was a very polished experience overall, and there was a lot of content for such a short timeframe.