Does anyone know how to defeat puzzle 1-28? I have been stuck there for…

Solution for Puzzle 28:

Put a green sphere at the end of the bottom and right strings.
Change the green color to white.
Change the white color to red.
Eliminate the bottom and right strings using red spheres.
Use a red sphere in the middle of the top string so it collapses all the way to the single 2 blue spheres on the left and eliminate the resulting string with a red sphere as well.

I'm stuck on Puzzle 35 for now, if anyone has tips. ^_^

I worked on #28 for days -- thx for the solution --