This is great! The pixelart looks awesome and the idea is cool and absolutely in the spirit of the jam. Took me a little to get the gameplay at first, but then I got it, quite intutitive. In my opinion the gameplay wold be really great if you had had time to make it a little more complex.
I found a bug where if I finish a run and wait until I get the character selection screen, I get the same character 10 times and can't start the game. Hope it helps!