I thought the game was pretty good. I liked the character designs. I think a big thing it would have benefited from would be more sound effects, for example on getting hurt, jumping on an enemy, collecting the diamonds/ freeing the notes. Also maybe a clear end of game screen, I wasn't sure that I had completed it at the end. Overall, I think it could do with some fleshing out, slightly more complex mechanics, and slightly more well defined/distinct themes for each world.
Nice job :)