Fun Maths

The following are some short and very cute math videos. While their beauty can likely be appreciated by everyone, they are meant for a general audience with minimal to no math background:

1) This video gives a beautiful animated describtion of how  topology (and particularly Mobius strips) naturally arise when trying to solve the seemingly unrelated and simple inscribed rectangle problem: Given a closed path in the Euclidean plane, the inscribed rectangle  problem asks whether it's always possible to find a rectangle with vertices located on this closed path. 

1) What is a harmonic function and why are they so cool?

3) This is a very short video that shows how the number pi miraculously shows up when performing a simple and seemingly unrelated physical expirement. It you are curious why this happens, it's explained in details here.

4) This is a nice video that explains the Gauss-Bonnet theorem to people whi are not familiar with differential geometry.