Fun game, I like it a lot! Good music, graphics are simple but look nice.
I like the controls - Arrow keys plus 1,2,3 seems pretty natural & easy to remember. (I didn't actually unlock the third spell, though)
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third spell auto unlocks with the,.. 5th or 6th treat I think. So loud like you went Trick a few times early on, (valid choice for longer spells),..
I've not found the best strategy myself yet, as I added the Trick increasing spell duration in the last few hours, to make it more of a choice.
Glad the controls felt right for you, hope you get chance to have another go, and see if you can be the first to make it to my secret win screen after phase 20 :P (impossible I think :D)