Very interesting idea. Great use of the theme. I don't know how the damage is calculated though. against the first enemy, I could pump magic attack to 42 and lower mana to 6 and everything else to 1 in order to one shot the enemy and get a score of 15900. However, on the next enemy, the pebble who has lower magic defense than the first enemy, I put magic attack to the same value and the lightning attack did much less damage. Are there hidden mechanics behind damage calculation? Making sure those are known are very important for making a game like this work since it's all about optimizing based on the situation.
Still, it's fun to theorize how to optimize score and the art and music are charming.