Love the artstyle. it looked really cute and coherent. It would be nice to make the range at which coins are attracted to the player much bigger. the different spells are pretty cool but you could make them even better if you add some sort of trade-off or combo system where multiple spells can interact with each other and the player gets bonuses or curses depending on the spells bought. I got to wave 13 where the enemies suddenly packed way more of a punch XD