Interesting game. Though I will say that using the mouse for it was kind of odd. Especially since rapidly tapping on your mouse is probably bad for the hardware.
For future games I would also suggest rewarding the player after they completing milestones. Seeing as how this game allows you to play any level you want, it's not a huge deal. But in future games you may want to add a level unlock system, in which case it'll be necessary for the player to get something out of it.
Regardless, it'll be interesting to see where you go from here.