Really fun game loop! A quick tutorial would be nice to show how to combine the spells, but once I figured out how, it was fun exploring the different combinations. I'd love to see it after some refinement, maybe adding in an overall goal number of enemies before the boss spawns, to build some suspense of what's going to happen? Maybe a minimap to see where you need to go? Maybe a system to develop your spells, and add more options? This is a really good base with lots of directions you could take it! Thank you for your game!