Wow, the concept is great! The pixel art looks really nice. The mechanic is simple but full of potential. For a gamejam, I think it's the perfect formula.
However, I had difficulty with most of the challenges. I think you could have given more situations/levels in which the player didn't die if he fail. This could have allowed him to learn the mechanic without being punished too much.
Overall the game is great, good job! :)