One star for making a platformer that functions, half a star for character design.
The backgrounds/platforms don't look great, the coins look fine but don't match the character, and there's so much going on color-wise that I can't say there's any visual distinction going on. I'm not going to comment on how short the game is, because it's obviously a proof-of-concept/early development stage, but there's so little content here that I'm pressed to wonder why you posted it at this stage. Also, it's weird to have an "exit" button that I can't interact with.
The game does control pretty well, though, and that's not easy to do. I think the platforms' own movement could use work, but the character did what I wanted him to do when I wanted him to do it and most beginner/early-concept platformers I've played don't do that.
Good start, would love to see a finished/polished version.