this is a really interesting concept! the upgrades here are good as are the enemies, all pretty solid gameplay. the main bit of feedback i'd give outside of that is that i think if this game were to be developed further, i think making synergies and specifically anti-synergies between upgrades would be a good step forward, since i think there's a lot of potential in making their placement in the (timeline?) more impactful as i don't think you have to think about that too much currently? impressive game overall and i enjoyed very much!