the Cray supercomputer was designed while Seymour dug a tunnel: Another favorite pastime was digging a tunnel under his home; he attributed the secret of his success to "visits by elves" while he worked in the tunnel: "While I'm digging in the tunnel, the elves will often come to me with solutions to my problem."

https://en.wikipedia.org/wiki/Seymour_Cray

I wonder if this was him being clever, or him getting carbon monoxide poisoning.

Dimethyltryptamine.

This aptly describes why I keep playing exponential growth games on my phone.

No mention of Coober Pedy.

Digging a Secret Tunnel - https://youtu.be/YOelRv7fMxY?si=mSfduDjj7SrmUCsk

More acting weirdly for ads and profit from what I gather there. Does he actually dig a tunnel / have someone dig a tunnel for him (like he has others cut out the concrete slab etc.) or does it stay at the stage of a hatch set on top of dirt?

I am also reluctant to invest time in watching a video, but he is quite impressive, at least to me. Starting out several years ago, he is digging by hand with the aid of a hydraulic poker that he fashioned. Removing the dirt and stones in buckets, welding reinforcing structure as he goes, etc.

The factory must grow, as any factorio player would say.