Overall a nice complete game, I couldn't get to the end of it sadly, will probably try again,
two biggest suggestion would be;
slowing the enemies down at the start, really unplayable and had to maneuver like prime Messi to get my first upgrade, after a few upgrade got a bit better
and I don't know much about optimization myself but the game (at least for my crappy laptop) got really laggy at the later stages, could look into how bullet hell games handle it
overall after the initial hiccup I started enjoying it! Kudos to you and the game!
checkout my submission if you have the time! peace!