Game's good, but let me nitpick for a moment :D.
Would've loved a perk system to go with the levels, there isn't much point to advancing without it.
I'd also like the enemies to have a different colour palette to distinguish themselves from the background.
I'd balance game difficulty with something else than the sheer amount of enemies - without making additional assets, you could make fast enemies, small enemies, more resilient enemies, and so on. Performance problems could be avoided this way.
Congrats on making a complete game for the jam, and this one's a solid entry!
(Also loved the takeaways in your devlog!)