Really like the soundeffects and animations that you added into the game, gives it that nice game feel.
However the fast bullets coming from the enemies doesn't contrast enough with the bullets coming from the bullet spawners, which makes dodging difficult. The fast bullets need to have a property changed so that it can be distinguished from the slow bullets. Maybe you can change the shape or the outline of the bullet or even changing the color (though it looks like you are going for a 1 bit theme here)
Nice use of the theme and screenshake which really adds to the feel of the game :)