Really cool and fun idea, only two suggestions?
1) Re-mappable controls. With my setup Saturn controller, A being jump and B being attack feels a little awkward.
2) Make the screen scrolling start a bit sooner than it does currently. As it is, the screen doesn't start moving until Maria's already nearly across the screen, and unless I'm hammering the attack button constantly it feels kind of cheap just rushing into enemies and getting hit immediately with almost no time to react.