Is anyone else having the problem of being invisible during and after fighting the Shadow in your nightmare? You can still defeat it if you have Dash, and then you get to keep your experience and skills, but it's seriously a pain.
Speaking of which, to beat the Shadow all you have to do is dash across the screen, wait in the corner while you heal, and then whenever he threatens you dash across to the other side again. When his boulders hit him, you dash across to collect the dark gems, and resume the process. And you can do it while invisible.