OK, Jay, this clip takes a bit of set-up. Basically, it’s a model of a factory-floor machine for moving pallets around a square assembly line. You put a pushing arm at each corner of the square and trigger them alternately in caddy-corner pairs. Some bright bulb figured out, however, that if you join two square tracks at one corner, you can do twice the work with only two more arms. Watch the intersection for a minute to confirm that the contents of the two square tracks are not mixed, which to me is counterintuitive. Here’s a video of the simple, single-square case that apparently started the trend. [via The Automata / Automaton Blog]