Too Easy!
This is one of my favorite games, BUT make it harder! I mean, like, you need, Easy, Medium, Pro, and then like Ultra or something. There should be like a harder boss at the end, like a clone or something. You know, where like you fight yourself; a copy that holds each of your moves... It could have a red aura, maybe it could be bigger, and maybe you could buff up its attack and defense power, possibly add a health regeneration. It needs a boss for sure, and there should be an Ultra mode, where you fight like double the amount of enemies as in Pro mode. THAT would be the real modification.