Hey!
Very nice game!!
The theme is excellent and the simplistic (semi) is very good, the atmosphere is all there!
Gameplay wise i would improve it by adding a tad more time to the music, its extremely punishing.
Even in the first level its super hard to get up there, the learning curve should be linear, start with easy and go up slowly. in addition to making the movement a tad more snappy, if you're counting so much on those music keys and every second counts u have to make sure its fast enough and jumps high enough.
I saw other people wrote "Checkouts", i actually dont think that checkpoints make sense if the levels aren't extremely long, fixing the learning curve / difficulty wouldn't require any checkpoints.
All in all - really awesome game, i enjoyed it :) (only got to level 2)