Entry #56 - concept; everything ( white square at the center ), in contained in the blue room ( blue square )
Entry #57 - if you can imagine the blue room in space with the door opened - exactly why the ray/beam hits the upside - hope you like this one - drop me a line for any changes you like to see
Entry #55 blue room - underground
Entry #54 two sided transparent walls of a room - yet can cast a shadow