I really enjoyed this game! I have some feedback tho...
Something to indicate which level you are on.
Cubes in background go in the direction of gravity.
Make big spinning spikes match pixel size.
Revamp jumping to make it so it follows how long player presses space
Make falling platforms shake before falling
Add extra platform.
MORE LEVELS!!!
Try to maybe make it a little less difficult. I found myself trying to make the character fly with switching gravity, and I don't really think that's something that should have to be done to complete a level.
The visuals and the game itself is amazing! I really liked it! Great game!