This post (https://vido.social/v/dzdd1UsL0D) made me think about a bit of a math problem. In this video, the train travels over most of its path twice before returning to its starting point.Are there any setups like this where the train travels over its *entire* path twice before returning to its initial starting point and direction? If not, why not?This is sort of related to Lionel and Roger Penrose's railway mazes (one pictured below from https://www.futilitycloset.com/2014/05/20/railway-mazes/, 3 more at https://stanwagon.com/public/mazearticlepreprint.pdf). Because direction doesn't matter in regular mazes, shortest paths traverse each edge at most once. In railway mazes since there are two directions, edges in shortest paths can be traversed twice. But unlike the physical train setup above, since you can make decisions in a railway maze, "cul-de-sacs" can be traversed in either the clockwise or counterclockwise directions (if the rest of the maze allows it).