Thinking Outside the Plane: https://www.metafilter.com/183649/Thinking-Outside-the-Plane

Interesting roundup of 3d solutions to 2d problems, starting with Tarski's plank problem: Can you cover a diameter-\(n\) disk with fewer than \(n\) unit-width strips?

Sadly, they missed the 3d proof of Desargues' theorem: https://en.wikipedia.org/wiki/Desargues%27s_theorem#Three-dimensional_proof

There's also a 2d-3d connection with Miquel's six-circle theorem but I think it goes the other way: https://11011110.github.io/blog/2006/03/22/miquels-six-circles.html