The gameplay was fine. I feel like adding other elements (ex. enemies) would have made it more interesting. The physics could have done with more work, as they were unsatisfying for me (to fix this just requires a lot of tweaking of variables and stuff). The art was overall pretty good, although I think all of the assets should be drawn with the same pixel size, for a more cohesive look. I think adding squash n' stretch to the character(s) would have helped a bit.
Other than that, you're doing great! Keep it up, but improve upon the way!