Sudoku (Japanese: 数独, meaning "digit-single"; originally called Number Place) is a logic-based puzzle where you fill a 9 × 9 grid so each row, column, and 3 × 3 box contains digits 1 to 9. The puzzle starts with some numbers given and has a single solution.
Similar puzzles appeared in 19th-century French newspapers. The modern version first appeared in 1979 as Number Place in Dell Magazines and gained popularity in 1986 when Nikoli in Japan named it Sudoku. It appeared outside Japan in 2004, thanks to Wayne Gould, who created a program to generate puzzles quickly.
History
Sudoku’s history traces back to 18th-century mathematician Leonhard Euler’s “Latin Squares,” with early number puzzles appearing in French newspapers in 1895. The modern Sudoku was invented by Howard Garns in 1979 as “Number Place,” published in Dell Pencil Puzzles and Word Games.
It appeared in Japan in 1984 as “Sudoku,” short for “Sūji wa dokushin ni kagiru,” meaning “the digits are limited to one occurrence.” Sudoku remains very popular in Japan, partly because number puzzles suit the language better than crosswords and are ideal for commuters.
Wayne Gould, a New Zealand judge, reintroduced Sudoku to the West after discovering it in Tokyo in 1997. He developed a program to generate puzzles, leading to Sudoku’s publication in The Times (London) and The Conway Daily Sun (U.S.) in 2004. Since then, Sudoku has become a global phenomenon, with the first World Sudoku Championship held in Italy in 2006.
Variations
While the classic Sudoku uses a 9×9 grid with 3×3 regions, many variations exist. These include smaller grids like 4×4 and 5×5 (called Logi-5), and unusual shapes featured in competitions. Larger and irregular grids also exist, such as the 12×12 "Dodeka Sudoku," 16×16 puzzles in Dell Magazines, 25×25 "Sudoku the Giant" by Nikoli, and even a 100×100 puzzle called Sudoku-zilla published in 2010.
Nonomino Sudoku (Created with AI)
Mini Sudoku
Under the name "Mini Sudoku", a 6×6 variant with 3×2 regions appears in the American newspaper USA Today and elsewhere. The object is the same as that of standard Sudoku, but the puzzle only uses the numbers 1 through 6. A similar form, for younger solvers of puzzles, called "The Junior Sudoku", has appeared in some newspapers, such as some editions of The Daily Mail.
Killer Sudoku
The killer sudoku variant combines elements of sudoku and kakuro. A killer sudoku puzzle is made up of 'cages', typically depicted by boxes outlined with dashes or colours. The sum of the numbers in a cage is written in the top left corner of the cage, and the remaining rules apply for this variant as well.
Other Variants
A three-dimensional Sudoku puzzle was featured in The Daily Telegraph in May 2005, and The Times also publishes a 3D version called Tredoku. Additionally, there is a Sudoku-themed Rubik’s Cube known as the Sudoku Cube, combining the classic cube puzzle with Sudoku rules.
Many other Sudoku variants exist with different layouts and solving rules. Some involve overlapping 9×9 grids arranged in unique shapes like butterflies, windmills, or flowers, creating complex, interconnected puzzles. Others change the logic needed to solve them. For example, Greater Than Sudoku adds inequality symbols (>, <) between adjacent cells in a 3×3 section, indicating which number must be larger or smaller, adding a new layer of constraint.
Another creative variant is Clueless Sudoku, where nine standard 9×9 Sudoku grids are arranged in a 3×3 pattern. The center cell of each grid is left empty, and these nine empty center cells together form a tenth Sudoku puzzle with no clues, making it particularly challenging—hence the name “clueless.” This layered approach tests solvers on multiple levels simultaneously.
