I would like to know how you designed level 20. I passed it using only the tp boomerang, but when I saw the pull rod, I got the feeling that it may wasn’t originally intended to be passed solely with the tp boomerang.:)
I create levels from an idea and then I try to find multiple solutions and change the layout a bit until I like it. On level 20 the teleporterang was one of the solutions but it's not the solution if you want to get solution with the limit of 3 throws.