Nice looking structure, but that loose block at the top is commonly called a Free Draggable and it can be used to win. Just pull it over onto the slider near the win, lift up to the top and tip it onto the win, ! It's best to fix draggables onto a slider. I tried to find the intended win, but it seems a case of pushing B off and being lucky with him landing on the red walkway. Is there a way to get a reliable landing?
Thanks for suggestions, really appreciate the effort but only solution is to push B off the edge like wise to get rid of R on the platform. I considered making the dragable block attached to something but crossing the platform will be impossible for B.