downloaded it, I like it!! the music is simple and not annoying. the graphics have a real nice feel to it. I was thinking this would be an excellent game for my kids, but I think it would be frustrating for them as it stands... but I've got some comments that you might find interesting
1) the first couple of levels are too tough and depend on precise positioning. I'd make them simpler. ironically your later levels look harder but are actually easier. make it easier... good players will fly through them, new players need an easier on-ramp. on level 2... make your fire a little smaller
2) I like the magic coin at the end for when you clear a level, but when I collected it first, I thought I had died.. a positive sound effect or fireworks imagery might work better than a cloud
3) your hand-grenades on later levels are hard to see compared to the background. more contrast would be nice... or simply blacker.
4) it's a pity you can't restart a level rather than just have to start again from the beginning... but that really is a design issue. some games are like that
so overall, very nice, very jealous best of luck with it.