Although the 9Ã—9 grid with 3Ã—3 regions is by far the most common, many other variations exist. Sample puzzles can be 4Ã—4 grids with 2Ã—2 regions; 5Ã—5 grids with pentomino regions have been published under the name Logi-5; the World Puzzle Championship has featured a 6Ã—6 grid with 2Ã—3 regions and a 7Ã—7 grid with six heptomino regions and a disjoint region. Larger grids are also possible. The Times offers a 12Ã—12-grid "Dodeka Sudoku" with 12 regions of 4Ã—3 squares. Dell Magazines regularly publishes 16Ã—16 "Number Place Challenger" puzzles (the 16Ã—16 variant often uses 1 through G rather than the 0 through F used in hexadecimal). Nikoli offers 25Ã—25 Sudoku the Giant behemoths. A 100Ã—100-grid puzzle dubbed Sudoku-zilla was published in 2010.
Imposing additional constraints
Another common variant is to add limits on the placement of numbers beyond the usual row, column, and box requirements. Often the limit takes the form of an extra "dimension"; the most common is to require the numbers in the main diagonals of the grid also to be unique. The aforementioned "Number Place Challenger" puzzles are all of This variant, as are the Sudoku X puzzles in The Daily Mail, which use 6Ã—6 grids.
A variant named "Mini Sudoku" appears in the American newspaper USA Today and elsewhere, which is played on a 6Ã—6 grid with 3Ã—2 regions. The object is the same as 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.
Cross Sums Sudoku