If you want to learn more about this stuff, the guy in the video wrote a great book called Origami Design Secrets (https://www.amazon.com/dp/1568814364/). It's certainly still the book about origami design.

For something that still touches on some of this stuff but is more beginner/child friendly, I'd recommend Jun Maekawa's book Genuine Origami (https://www.amazon.com/dp/4889962514)

There's also the OSME books (http://osme.info/) which collect origami related papers.

His previous book "Origami Design Secrets: Mathematical Methods for an Ancient Art" (https://www.amazon.com/dp/1568814364) was also really, really interesting.