Great game. As others already stated, the art is cute (I like that magical girl vibe) and the level design is neat, I personally love the different ways you can use the transformation powers. I enjoyed it a lot! Already shipping Rose x Serena.
I am playing with a QWERTY keyboard, the controls are good overall, but I would rather set the Up arrow for jumping instead of Z, that way the Z key could be used for one of the available powers. It is just a suggestion though. About the bugs, the only one I found that could be important is that after getting the Wind transformation spikes don't hurt.
Nice one. Looking forward to the future versions!