Spoiler: Correct solution? After making R go around diagonally, I directed him into the rail with the slider. While he was stopped, I kept trying to push him until he went to the white squares.
@Frenzies That's it ! Spoiler: Another solution It is possible to push R without the rail, but the timing is so demanding that it is almost impossible. It can happen if you are lucky though. That's why I made the rail. It was tricky because it has to allow R to walk on the white squares but not on the black ones...
@Frenzies There is another way to do it, maybe better: There is no strange floating roof this way (I just figured it out now).
