Sudoku

Fill the 9×9 grid so every row, column and box holds 1–9. Fresh puzzles across difficulties, timed.

Sudoku is Swiss before it is Japanese. Euler's Latin squares are the ancestor, the modern form appeared in an American puzzle magazine in 1979 as Number Place, and Nikoli's renaming in Japan and Wayne Gould's newspaper syndication in 2004 made it global.

The known result worth quoting is that seventeen is the minimum number of givens for a puzzle with a unique solution — proved by exhaustive computer search in 2012. No sixteen-clue puzzle with one solution exists. Difficulty, though, is not about clue count but about which solving techniques a grid forces you to reach for.