Cool game! The minimap is super useful and the upgrades are nice and I'd even say essential to get, i agree with others who said that the first level was a bit too hard, not because it's hard to dodge but because of the rate of shooting since you can't keep up with the amount of enemies spawning. Which lead me to find that with one bullet i could hit more than one enemy at once, it helped a bit but i wasn't sure if it was a intended behaviour for the projectile.
Cheers ;)