谁在乎拓扑学？（旧版）

An older 3Blue1Brown video on why topology matters, built around the inscribed rectangle problem. It walks through how tori and Mobius strips appear in the solution. The channel later replaced it with an updated version.

Why HN likes it: Fans name it as a favorite 3Blue1Brown video, praising its detective-story treatment of the inscribed square and rectangle problem.

“A particular favourite is the one on the Inscribed Square Problem”