Kartik Prabhu liked https://www.youtube.com/watch?v=d-o3eB9sfls because Pretty neat way to think of the Basel problem with lighthouses and the inverse square law!
Kartik Prabhu liked https://www.youtube.com/watch?v=NaL_Cb42WyY because lot of awesome number theory here — primes, factorisation, Gaussian primes, character functions — pretty neat!
Kartik Prabhu liked https://www.youtube.com/watch?v=QJYmyhnaaek because I never realised that you can get all Pythagorean triples from complex numbers!