Pretty cool.
It's a fun game and it looks like you've put quite a bit of effort into it. The characters are cool but it'd be better if there were different enemies and maybe a few different ways to attack them. I like the simple background layout but it'd be cool as well if they changed completely for different levels, not just in colour. I think it'd be cool if there was a bar on the bosses to show their remaining life and although I liked the music, a choice of a few different tracks would be cool. Overall, definatly worth playing, good job.