Nicely done! This is a great, small scope experience for a game jam game.
Because this is a jam game, I think you could have cranked up the power curve considerably. There seems to be little difference in player and enemy strength between waves. The idea of difficulty increasing mostly just by a larger number of enemies with the same behavior is a little boring by itself. Making the jump in player power and enemy strength between levels lets players get more bang for the few minutes that they might be playing your game.
Once I figured out that you can wrap around the map, but enemies can't, the game became pretty easy. Still cool though. The controls felt a little wonky when trying to change directions, but were otherwise solid. I had fun dodging between all the bats and rounding them up before slowly chipping down the swarm for a victory.
Congrats on finishing this in just a few days!