Over the years we have seen many marble machines, but this one on the [Karakuri channel] (hit CC for subtitles) on YouTube is somewhat special, as it uses Geneva drives to turn the motion of the steel balls going around the circuit into random movement of a marionette. The Geneva drive type of gear mechanism normally converts a constant rotary motion into intermittent rotary motion by having a singular pin on the first wheel drive the second wheel. In the demonstrated mechanism, however, the pin is replaced by the steel balls, which are only intermittently and randomly present because of how each steel ball picks one of four paths, one towards each Geneva drive.
This is a companion discussion topic for the original entry at https://hackaday.com/2024/03/12/randomly-move-marionette-with-steel-balls-and-geneva-drives/