Looks like a really nice concept!
The graphics and audio are the strongest parts, and both work very well together. The music is great.
I found it quite frustrating to understand what was happening at first - insta-death when you are hit by an enemy; and it goes right back to the title screen without explaining anything.
Similarly, there is no feeling of reward for killing enemies as they just disappear off the screen.
The jump mechanics are very "floaty" and feel a little clunky.
I don't think this game would take much, just a bit of polish, and it would be great fun.