The presentation here is fantastic love it! the UI of the choosing the new spell you want is quite nice and I like the little intro at the beginning and the death screen. the art work is stellar as well! the sound design is very good as well and I like the creepy sounding voice.
I like the theme is used in a meta way as costing real life time of drawing the spells that's quite clever! I appreciate that you have given a good margin of error if you don't draw it bang on the dots, that's very helpful. The tension of trying to draw in time when each wave of enemies are closing in creates a great level of tension.
Though I find it a little tedious to go back an fourth with selecting the different spells from having to change which button i'm pressing too fast, I would've preferred if you could still press left mouse button to select the different spells, but have the spell menu outside of the drawing detection area so it doesn't over lap, and having the cancel spell mapped to something on the mouse instead of keyboard for faster reaction time pressing it from the player.
Overall very high quality stuff, Excellent work! : )