There are numerous ways to vary the basic Sudoku format. Yet, only a few variations have developed a loyal group of supporters. Most variations are regarded as a curiosity.
There are many ways to vary a Sudoku. Here are only a few examples:
- Change the size
- 2x2 Shi Doku
- Replace boxes by other shapes
- Add extra constraints (Sudoku-X, Windoku, Asterisk, Even-Odd, Non-Consecutive, Consecutive Puzzle, Sudoku-DG)
- Replace givens by alternative clues (Killer, Greater Than)
- Replace digits by letters, symbols or images (YourDoku, Wordoku, Picture Sudoku)
- Merge several constituent puzzles (Gattai, Samurai, Clueless)
- Use non-rectangular cells (Hanidoku)
To complicate things, a puzzle maker can combine several of these alterations.
These often appear in newspapers or feature in dedicated puzzle books.
- Killer | Sum-Sudoku | Samunamupure
- Given numbers are replaced by cages labeled with the sum of the digits inside the cage. This is by far the most popular Sudoku variation.
- Jigsaw | Nonomino | Squiggly | Irregular Sudoku
- 3x3 boxes are replaced by regions with an irregular shape.
- The 2 diagonals also require digits 1 through 9.
- Windoku | Hypersudoku | NRC-Sudoku
- There are 4 additional 3x3 boxes in the grid which must also contain digits 1 through 9.
- Samurai | Gattai-5
- A puzzle with 5 partially overlapping Sudoku grids.
There appear occasionally in newspapers, but have dedicated websites and appear on a regular basis in Sudoku variant books.
- A puzzle with 9 Sudoku grids where the center nonets form a 10th Sudoku grid.
- Flower Sudoku
- A puzzle where 4 Sudoku grids each overlap 6 boxes of a central Sudoku grid.
- A puzzle with hexagonal cells that must contain a consecutive series of digits.
- Greater Than
- A puzzle where the given digits are replaced by greater-than signs.
- Consecutive Puzzle
- A puzzle where any 2 adjacent cells containing consecutive digits are marked on the border between the cells.
- A puzzle where 2 adjacent cells cannot contain consecutive digits.
These variants are less common.
- A 3D implementation of a classic sudoku. Sudoku3D is a single puzzle on a surface of 4x4x4 cube.
- An ordinary Sudoku, except that the starting position contains pencilmarks instead of givens.
- Sumo | Gattai-13
- A puzzle with 13 partially overlapping Sudoku grids.
- Shaolin | Gattai-25
- A puzzle with 25 partially overlapping Sudoku grids.
- A 3x9 grid with a sum column as an additional constraint.
- Sudoku Variants wiki at the World Puzzle Federation web site