So great! A lot of those are mechanical styles I'd never seen before. 😲 So these are made using LEGO plus other components, then..?

For anyone who wants more, Rube Goldberg machines are often a genesis point for 'marble machines.' Two of my favorites are from the game show PythagoraSwitch and the wonderful Wintergatan music machine.

(the latter two links are YT videos, btw)

How do they prevent buildup at bottlenecks?

Pita gora suichi?

Speechless. I have no speech.