The puzzles were good, and I like how the death mechanic was switched up midway through the game. Normally changing the rules midway through the game would be a bad thing, but the game's short enough that you can get away with it.
I was a little disappointed when I found that there were only two Expert Rooms, and the most puzzling thing about the game was probably the ending. =P
If you're interested in seeing my impressions first-hand, I just finished up a let's play of the game, which can be found here: https://www.youtube.com/playlist?list=PL9kd-uZiIb99tSi8Xp45d_MNA-yxdUXPx