Wow, that was really fun and surprisingly addictive. Beautiful art, audio, and very fun gameplay. But there were a few things I think you can do to improve.
Enemy variety would vastly increase the replayability of this game. That and attack variety/items. More stuff to spice it up.
Challenge wise this game was not particularly hard. I think making it a bit harder would really make it more fun. I got to 31,600 (see pic) and gave up because I got bored. I think there's also a bit of a prevailing strategy that makes the game really easy: hugging the bottom of the screen. Since enemies don't spawn there, the player can just sit there and wait for the right spells while dodging enemies and racking up a huge score.
Overall though this game is a really fun and addictive arcade puzzle/strategy game. Great job!