Ask HN: Whats the smallest code that you looked at and said wow that's so clever

BUSINESS CARD RAYTRACER https://fabiensanglard.net/rayTracing_back_of_business_card/

Tupper's Self-Referential Formula https://mathworld.wolfram.com/TuppersSelf-ReferentialFormula...

Duff's Device.

https://en.wikipedia.org/wiki/Duff%27s_device

there lots of examples, in many languages, of Dijkstra’s Two Stack calculator. this one is in ?javascript? https://switzerb.github.io/imposter/algorithms/2021/01/12/di... a very elegant piece of code

Not a code, but an AI-Like solution for any programmer's problems on windows systems.. ALT+F4.

(But generally, I think the lambda functions of python is kind of clever, short code. Some solutions based on lambda functions let me shiver in respect)

any self-replicating quine is amazing