Nice idea, but pretty difficult puzzles. I was struggling with the one pictured in your screenshots, but I solved it. Only to realize now that you were giving away the solution in the screenshots. I made it to the level with the controls in the square in the middle of the level.
Being able to restart with R would be nice as well as reverting (undoing) with Z. Some indication of which portals are connected to which would also be useful. I'm not sure if they were bugged in the last level I played or that they were intended to work the way they did. It was just contradicting how they worked in the levels before it.