Assuming that things such as animating the character are to come. The most important item is to have the camera a lot lower. Whenever you jump, the floor is no longer visable. And an important thing missing is an ending. The fifth level doesn't complete, and instead plays the failure sound and start over again.
But non the less, it is really difficult to join a gamejam, and actually finish something. So don't take these critisms harshly.