It's not very well made :/
The sprites and textures in general look kind of cheesy, sometimes you don't realize that you are facing a platform (clouds) or even that there are enemies (just didn't take notice of the birds until they killed me). The level design itself is actually just annoying; at the part with this shooter-things
you couldn't advance without getting hit at least one time at every jump.
It's actually just kind of... a jumping platformer with a lifebar instead of overwhelming gameplay.

It functions. Controls are alright. Hitboxes are clunky. Design definitely needs work. Wasn't apparent that clouds were platforms or stomping on enemies works.

Not bad. If this is just a concept I could see this being a genuinely fun and challenging game. I hope you release a completed version and improve on this. The only things I can think of that you could improve on is the visual look of the game and add some animations to the characters.