The base idea is nice, but there's a rough start and feel like it introduces too many spells at once.
IMHO the game should add just something like just 3 spells at start, then slowly add more so the player can memorize them more easily.
It wasn't very evident that I needed to use a specific spell only to actually win, probably there could be some big flashing sign "YOU NEED TO USE THIS SPELL IN SPECIFIC" at the first round ><.
Also I think it's some kind of game dev sin that the same version of an enemy will need different spells to defeat. Like one of the core principles of a game is connecting visual cues, "this wolf-looking enemy was vulnerable to fireball last time I fought them, next time I see one like them I should use fireball again." Enemies that share the same sprite should share the same specific weakness.
Otherwise a good combination of graphics and music with a nice gameplay loop after you actually memorize the spells, see how far you can ge, great job!