Marble Machine X is an ongoing project by Martin Molin of the band Wintergatan to create an amusingly-complex mobile marble-powered instrument.
His videos documenting the project receive hundreds of thousands of views, and plenty of enthusiastic and helpful feedback. In this video from September 2018, he shows off an earlier stage of the build, and emphasizes various safety measures he added in response to helpful Youtube comments:
The videos in the series find a great balance between being edited to remove the boring parts, while also being quite informative about the fine details of the build:
You can support the project via Patreon, or by purchasing merchandise here.
(Via Andrew Fraystive.)