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Penrose Unilluminable Room is a room with mirrored walls that can’t be fully illuminated by a single point source of light. I thought I was the first person to build one but Action Lab beat me to it:

• I Made a Real-Life Unilluminable Room

Here’s Nils Berglund’s channel:

/ nilsberglund

Alex Bellos’s elliptical billiard table can be found here:

• Elliptical Pool Table – Numberphile

You can buy my books here:
https://stevemould.com/books

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