Matthias Wandel has built a simple computer (an adder) that uses marbles. The story of how he had to add extra pieces of wood to help guide the marbles, so that they wouldn’t bounce out and throw off the computation, reminded me of the apocryphal stories of early programmers having to literally “debug” computers by removing moths or other insects that had become trapped in the relays.

Be sure to watch the video (found at the bottom of the page) to see it in action. Oh, and don’t feel shame if it reminds you of Plinko — that’s the first thing that came to mind for me too.

Thanks to Seth Ladd for the link.