Impressive game, good job!
I find the game hard, but not because of the level design, but because of the lack of feedback:
- I’d like to know when I loose a life: a little sound and visual info (like a little -1 that pops close to the character) so I know that I need to look for a chest.
- Being killed for staying in the air for too long feels frustrating: It would be awesome to a visual indicator that lets the player know that he’s playing with fire (and he can actually do it on purpose!). I can really imagine the character going too fast and taking fire because of the friction: that could be a good visual and diegetic indicator. :-)