Sudoku also sudoku or Su Doku

a number placement puzzle consisting of a grid of nine 3-by-3 squares, in which the numbers 1 to 9 must be placed so that each row, column and square only contains one instance of each number

It's hard to believe that only just over a year ago, the word Sudoku could be unknown to the majority of English speakers. A year later and the Sudoku number puzzle is as familiar as the daily crossword, a phenomenon that has swept through Britain with the same explosion of popularity that the Rubik's cube enjoyed in the 1980s.

the Sudoku craze has spread like wildfire through Britain, and is now entering the domain of terrestrial television

A Sudoku puzzle, also known as Number Place in the United States, consists of a 9-by-9 grid made up of 3-by-3 sub grids, sometimes known as regions. Within each region, some numbers, referred to as givens or clues, are provided in certain cells. The aim of the puzzle is to ensure that in each row, column and region, there is one instance of the numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9. Sudokus appear in various levels of difficulty according to how many numbers are already filled in.

Sudoku puzzles have proved immensely popular across a wide range of generations and nationalities, possibly because they require no specific mathematical skills and eliminate the language barriers associated with conventional puzzles like crosswords. The craze has spawned a number of variations on the same theme, including an alphabetical puzzle aptly referred to as Wordoku. At the end of August 2005, The Times newspaper in Britain launched the Killer Sudoku, originally called the Samunamupure (literally 'sum number place') by its Japanese inventors, which has the added complexity of requiring digits within inner boxes to add up to specified numbers.

The Sudoku craze has spread like wildfire through Britain, and is now entering the domain of terrestrial television as the BBC plans to run a series of lunchtime shows in the two weeks before Christmas, entitled Sudo-Q.

Background – Sudoku

The term Sudoku is based on the Japanese words su ('number') and doku ('single'), though the puzzle's origins aren't strictly in Japan. The first puzzle of its kind was entitled Number Place, created in 1979 by freelance puzzle constructor Howard Garns, and subsequently published in New York by the specialist puzzle publisher Dell Magazines. Five years later it was adopted by Nikoli, a Japanese publisher specializing in logic puzzles. Here it was introduced as Sūji wa dokushin ni kagiru, which can be translated as 'the numbers must be single', a description later abbreviated to Sudoku and now a trademark held by Nikoli in Japan. Sudoku's journey to Britain is allegedly attributable to Wayne Gould, a retired judge from New Zealand who bought a book of the puzzles during a trip to Japan and was immediately hooked. After a communication between Gould and Michael Harvey, features editor of The Times newspaper in the UK, the first Sudoku puzzle appeared in The Times on 11th November 2004.