Love the visuals on this one! Did you use vector graphics for this game?
The progression with the upgrade system is quite nice. It's what made mee keep playing. But the early stage of the game feels to much of a grind to be honest. Also the shooting mechanic is a bit weird as there is so little control over it. It's already hard enought trying to dodge all the attacks. I felt no much use in the ability to reverse my aim direction. I would try for this game to have the bullets go in a steady direction, where the direction can be rotated holding the left and right mouse buttons or mouse movement. This instead of having it rotate on its own with only the ability to reverse the rotation. In addition add an upgrade to increase aim speed.
The sounds and music were quite nice as well, though it took me a while to figure out what each sound means.
Overall this game feels really polished.