A Crap ton of Marbles.
11,000 according to the video description to be sure. I’m sure there are more there, that large trey at the end seemed like the markers were past the 10,000 point before it flipped. There weren’t that many different paths for the marbles to go though. I think it would have been more interesting if there were a couple extra paths, or some more advanced engineering tactics employed.
Oh well, take a listen, and a watch, and be amazed!