Not bad for a prototype!
The gameplay,while pretty casual,can also be tricky. Not only you have to watch and time your jump,you gotta also look out for your fall. Nice addition there.
I especially like that the clouds have multiple faces,thats definitly a plus point.
On the other hand,this game in its current state is pretty boring. You should add multiple sound effects and some backing tracks,listening to only one sound repedatly is pretty nerve-killing. You should also some new content. (ex.backgrounds,enemies,levels,etc.)
Definitly not bad,keep it up!