I like the concept but it definitely needs more baking. The level progression seems a bit shoehorned and ends up being tedious. I think it's a good starting point and had there been more time or man hours able to be put into it, it could come out rather well.
One improvement suggestion I'd like to offer for the potential future is consequences from having the enemies on the screen. Perhaps there were plans for it already that went unrealized but at the current state, they do just sit there waiting to be shot.