Amazing game!
I found that replaying it was pretty fun, although it got a little tedious after a few playthroughs. I'd suggest making the powerup unlock thingy happen sooner, and make the prices for the unlocks lower, since I started to lose interest before I had enough to unlock anything.
I'd also suggest making the view range bigger, since a lot of times, I couldn't dodge or lead my shots since I couldn't see the bullets or the enemies.