A puzzle, Probably created by an American in 1979
https://en.wikipedia.org/wiki/Sudoku
Sūji wa dokushin ni kagiru (数字は独身に限る), which can be translated as "the digits must be single", or as "the digits are limited to one occurrence" (In Japanese, dokushin means an "unmarried person")
Cracking the Cryptic does YouTube videos solving them (and pencil puzzles)
GAS Leak is a collection of puzzles