I'm glad you liked my game that much :)
Regarding spell selection. I have an idea, but it's suited for a different genre that this game could turn into: you could have a limited number of available spells (for example, 6), then the selection of stencils could be assigned to hotkeys. Of course, this set could be switched between waves. I repeat, this isn't for the current version of the game. But in terms of frequency — to make it to the end, the player would need to remember at least a couple of spells, so they wouldn't waste time choosing a stencil