The idea is super cool, and the game itself is incerdibly polished! I love the character animations.
I've found it a bit tough. Partly because I was just staying in rhythm even when I was on lava (I'm too used of Crypt of the Necrodancer), which was just making me step on lava again! :P But that's actually part of the puzzle I think, and overall my main regret is the absence of checkpoints. (also I'm not a fan of the changin rhythm, but again, that's Necrodancer habits ^^')
Also, the music is awesome! It's a great selection of songs, and the covers are excellent! Very good job on that.
Overall it's a really fun game, with tons of lovely details. Well done!