The idea of a tower defense platformer is quite interesting, but the game is really hard. I think the jumping and the UI needs improvements (it is hard to know when you're gonna lose). I loved the aesthetics: the pixel art and the animations, the sound effects and the music (which reminded me of Fez)).
I would have liked that the platformer component of the game was used not only to get crystals, but as part of the tower defense in itself. What if the player had to build turrets in the ground and carry them to the top.