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Rules and Examples
Hanidoku is a new variant of Sudoku with an extra dimension. Each row, up and down diagonal must contain a range of
consecutive numbers between 1 and 9. Because the rows and diagonals are not all the same size, there is an extra
challenge to find out which range of numbers must go into each line.
The varying ranges prevent the player from using all the familiar Sudoku tricks. Solving these puzzles requires
new ways of logical thinking, which includes dealing with uncertainties. Difficulty varies from gentle to diabolical,
depending on the solving strategies required. We guarantee only one solution.
The given numbers will eliminate candidates for that number in 6 directions. The usual strategy is to start with
number 5, because it is required in every row and diagonal. From there, you work your way from the inner numbers (4,6) to the
outer numbers (1, 9).
- Naked Singles. When a cell has only one candidate left, you can place it in the cell.
- Range Trimming. Use placed numbers to determine the range for a line (row or diagonal). A row of size 5 that
contains number 3 can no longer contain numbers 8 and 9.
- Requirement Check. Many solving strategies can only be used when you are certain that a number must be
placed in a line. When a line contains number 8, numbers 6 and 7 must also be present.
- Hidden Singles. When a number is required in a line and there is only a single candidate for it, you can
place it in that location.
- Incomplete Ranges. When all candidates for number 3 are eliminated, the range must start at 4 or higher.
All candidates for numbers 1 and 2 can be eliminated.
- Triangulation. With only 2 candidates left for a required number in a line, all candidates that form a
triangle with these 2 can be eliminated. This strategy is often available.
- Pairs and Triples. Naked pairs and triples can be found in lines the same way as in regular Sudoku.
Hidden pairs and triples are rare and can only include required numbers.
- Advanced Strategies. Some advanced Sudoku solving strategies can be adapted for Hanidoku, while others are
still undiscovered. Because Hanidoku is a new puzzle format, you have the chance to discover these unknown solving
More advanced strategies, which you will encounter in our diabolical puzzles, are explained at the