A pair of compasses
BBC educational programme: “Be sure to set your calculator to maths”. Complete with pictures of cats.
This is the first part of an excellent BBC series called Look Around You. Thants!
Meanwhile, Essiness, AKA Slim Dorky, AKA Dr. Stephen Sawin at Fairfield University, raps the Bolzano-Weierstrass theorem. He even ends with a traditional “I’ll leave you with this exercise: to prove it in Rn” :)
He’s back with Perelman’s proof of the Poincare conjecture:
More on his page.