Hi, thanks for the feedback. I was originally planning to add more upgrades that would cost the same resource as you progressed + more enemies, but the time limit got to me. So a few rounds before submit time I decided to finish the core game (shooting + enemies in several waves) and call it.
All the things you pointed out are reasonable, but my time management wasn't good enough. I hope I can improve for the next jams.
Thanks for playing!