Great game. its a good platformer, altough I feel that if you add checkpoints it will be too short. The artstyle is very good, and the game controls are very responsive.
I dont quite like having to install the game, generally for GameJams I feel you should make your game as portable as posible (preferably a web Game, although a portable game is good enough). this doesnt affect the quality of the game, but it could be a detriment if somebody is doing a rating spree and sees that they have to stop, download and install your game instead of just playing it either on the web, or a portable version (they are more likely to ignore this game to avoid the hassle).
Overall, excellent job :D