First 6 puzzles were straightforward. But the 7-th was already hard for me.
You need to keep a good momentum to reach the 3-rd star from the bottom of the screen in the 7-th puzzle. So the curves you draw should be smooth and round. And honestly I don't even know if it is possible to beat all the puzzles.
I would rather prefer to have some additional mechanisms, like springs, portals, accelerators, etc.