The story begins over on the 3D printing subreddit, where the amazingly-named SturdyMilk05254 had an epiphany. See, they had created this wonderful project where marbles are brought to the top of a 3D ...

It consists of just six 3D printed ramps which the marble tumbles down in just a few seconds. However, the real magic is in the mechanism that restores the marbles from the bottom of the run all ...