Very cool game!
I like that the game lets you stop the ball and throw it again.
The extra obstacles
A good feature you could consider adding is a free-camera mode to allow the player to spectate the level ahead.
The difficulty felt like it increased a bit too much on the later levels. Sadly balancing game difficulty is a hard thing in general.
One idea i would propose you is to watch other people play your game and see where they struggle, then try to find why.
For me the hardest obstacle were the rotating spiky fans.
I found it a bit hard to aim properly (more precisely, to pick the correct force so that it passes along multiple rotating spiky fans) and i had a hard time when there were a lot of these.
In my short observation (i finished level 17) most of the difficulty came from having a lot of obstacles that i had to overcome until the next goal/checkpoint. Maybe you can add multiple difficulties that modify the number of checkpoints on levels? (example: easy - a lot more checkpoints; casual - more checkpoints; hard - current checkpoints; insane - no checkpoints at all)
I believe i found a visual bug where when you grab the moving ball to throw it again the camera moves but the aim-line doesn't.
Attaching cropped screenshot below:
Overall the game was very enjoyable and fun to play.
Thanks a lot!!! :D