Love the music and visuals and the challange. The difficulty curve could be a bit smoother, the spike colliders a bit more lenient and the jump bar closer to the player, but other than that it's my favourite entry so far.
(4 crystals, jumped 1950 times)
Spoiler: The secret room(s) (I found just one) are really neat. Also, screw the aggroed phase of the boss ge gets just too trigger-happy...