What Problems to Solve (1966)

Thanks a lot for posting this. I highly recommend having a look into the mentioned flexagons. This is a child toy where Feynman laid the mathematical background and it is very fascinating toy which you can easily build yourself. Try it out - it is really fun. No child required except yourself :)

I didn't realize it until I searched for it, but as a kid I did have one of those. An M.C. Escher one (a quick search found exactly the one [1]). My aunt got it for me when I was little and I was fascinated by it. Fond memories.

[1] https://www.jacobsurovsky.com/researchanddevelopment/2020/8/...