I really like the idea of switching spells on the fly to damage different enemies. The progressively harder repeated boss fight was cool, too.
I think you could have gotten a little more out of spell switching by placing the player in situations where they need to switch more often (like an arena with several enemies rather than hallways). An extra ranged enemy would have added to this as well, since there would be a reason to prioritise defeating one enemy first.
The intro confused me a little bit. I thought I couldn't damage anything with the white spell and needed to run past the enemies to find the charms first (maybe just clarify that you need to match the colour, so it becomes more obvious).
Overall, I had fun, though, and played through to the end :)
Edit: I just realised how similar the names of our games are!