I managed to get to wave 11. The gameplay is simple but actually pretty fun and engaging! It's easy at the beginning but the difficulty ramps up surprisingly fast. One or two more enemies throwing off the usual player strategies could work really well with this.
A minor nitpick: It took a while for me to understand that the lighning bolt was a powerup! I thought it was just a bugged sprite leftover from one of my attacks at first. Making it look a bit different could help, especially since it's arguably the strongest powerup.