The game was to easy for me, but my sister enjoys it. But since this game has highscore it should be easier to die (for example adding more enemies after next level). I don't know how this happened, but when I tried to shoot some enemies even if I hit them I didn't destroy them and if I shot somewhere else it destroys that enemy (maybe colliders and sprites weren't at the same position for those enemies, but it's just my quess).
So I started with things I didn't much like about this game, so now is time to tell you what I liked. Movement and shooting was fast. There were nice effects when an enemy was destroyed. I also liked the upgrade system, as there were some kind of progression in this game.
Good job.