Art is good. The background is a bit dull, though. A basic paralax background make sideview games look way better with little work (just 2 textures with bamboos for example, and a 3 lines script).
The gameplay is ok but the controls are not very intuitive, and some of them unecessary. For exemple why do we need to press 2 keys to jump? Just make it automatic (like in Mario games). This is especially true in a game jam where you can expect that most players will not be used to platformers and pretty bad at it.