Fun game! Played it on my laptop, and placing enemies strategically and fast enough for them to be challenging for the AI was really hard. I don't think a single one managed to hit the AI even once, up to wave 11.
Also for the upgrades, I got one to improve my abilities for when spawning: the "decrease radius" one. Not sure if there are others, but perhaps something to improve upon is to add more for when you're spawning monsters, and also if you already have others, to balance the rate at which they appear and not just show upgrades randomly. Also at one point early on I had 3 self-sabotage upgrades that were "Take double damage".
But these are just balancing stuff, which I know isn't a priority during a Jam. All in all, I definitely think this idea has potential. It enjoyed playing it, it was super-fun!
The UI could use some polish, but it's clear what stuff are and it works and I didn't encounter any issues playing it.