Check out https://en.wikipedia.org/wiki/Billiard-ball_computer https://en.wikipedia.org/wiki/Billiard-ball_computer It's theoretical but there are some great id

Check out https://en.wikipedia.org/wiki/Billiard-ball_computer https://en.wikipedia.org/wiki/Billiard-ball_computer It's theoretical but there are some great ideas in the general area of mechanical reversible computing.