The game is too flat.
The background graphics are uninteresting, the characters are OK.
The stages repeat after a while with just a palette swap.
The gameplay suffers a lot as there is no challenge. Press the rapid fire and wait the enemy to come if he is alone or choose the height of the first. Move around if they get close together as you hit only one, and repeat.
Music on the other hand is really good.
I wish you had the time to work on it a little bit more on the last 9 days.