Fun concept. Reminds me of an old mobile game I used to play called Graffiti Ball.
The dropdown menu to select a resolution scrolls REALLY slowly when using the mouse wheel, and it's kinda hard to tell if vsync is enabled or not. There's a typo in the first tutorial. "To goal" should be changed to "The goal."
There are some minor physics problems, such as balls spinning forever inside green circles, and balls occasionally sticking to the bottom of lines. Also, I noticed that occasionally when I hit the "Start" button twice without changing the level at all, the ball moved in two different ways. Is there some sort of random number generator being used?
Fix up the issues I mentioned above and I think this could be a fun little physics puzzle game.