For the limited time you had on making this, it turned out pretty nice. Art is clean and simple, music fits the minimalistic style well and the game mechanic is quite fun.
Personally, I would've put the indicator that switches the color of the balls somewhere else instead of on the skull since it's something that affects the whole area and not the skull itself. In the instructions, you forgot to mention that the skull reaches farther by holding down the mouse button or spacebar longer.
Other than that, it's a neat little game jam entry!