After 50+ years, a trio of codebreakers solves the puzzle and earns a nod from the FBI.

It only took a couple centuries.

A challenge that the famous puzzler Martin Gardner put forward long ago remains open

The missing square puzzle is an optical illusion used in mathematics classes to help students reason about geometrical figures; or rather to teach them not to reason using figures, but to use only textual descriptions and the axioms of geometry. It depicts two arrangements made https://t.co/Rib1zd4a7H