A little history
The modern puzzle was created by the American Howard Garns: in 1979 Dell magazines published it under the name Number Place. In the 1980s the Japanese publisher Nikoli made it popular in Japan and named it sudoku, from a phrase meaning “the digits must be single”. The global boom came in the 2000s, when newspapers around the world started printing it.
Why sudoku isn’t math
Sudoku doesn’t ask you to add anything: the digits are just nine different symbols. Pure logic solves it: eliminating options, finding contradictions, holding several hypotheses in your head. That is why sudoku suits even people who dislike numbers.
Basic solving techniques
- Naked single. If only one digit fits a cell, that is the answer.
- Hidden single. If a digit can go in only one cell of a row, column or box, put it there — even if other digits also fit that cell.
- Pencil marks. Note small candidate digits in each cell. On medium and hard levels you can’t do without them.
- Naked pairs. If two cells in a row can only hold the same two digits, remove those digits from the other cells in that row.
Mathematicians proved that a sudoku with a unique solution can’t have fewer than 17 starting clues. It took an exhaustive computer search, published in 2012.
Benefits for your brain
Sudoku trains logical thinking, attention to detail and sustained concentration — one puzzle takes anywhere from a few minutes to half an hour. It is a good “slow” workout to balance fast reaction games. In Cabe it pairs well with the section’s other logic puzzles: the Tower of Hanoi, Magic Square and the 15 Puzzle.