This is an interesting base for something - the level design was pretty good - I just don't see how it relates to the theme.
I really disliked having to jump with space since I was shooting with X but I unexpectedly got used to it and then found the character control to be really smooth (except for the fact that you run at the same speed as the bullets).
I don't have any complaints about the audio - I thought it suited the style of game perfectly.
There's not much else I can say that hasn't already been covered by others. I think you could make a good platformer with this if you wanted to.