@Doctorf Spoiler: How to ? Combine some R-Bots with metal objects. They have to walk in different directions
@Doctorf - The blackening effect is actually a normal shadow feature of the game, but in this case it is as a result of the outer metal block layer disappearing, which is a bug artifact of the game. Whenever you try to connect four Rs (that face in different directions) together with connected metal blocks (instead of individual eyes), the R bots and all metal blocks connected to them will disappear when you try to start playing the level. It could be that the game engine is not able to resolve which direction the bots and the metal should move and thus it simply gives up and makes them all disappear. The shadow affect is normal though, but since the outer layer of metal blocks in this case disappear, the interior brick and unconnected metal blocks are so shadowed that they appear black.