SudoCue - HaniDoku Introduction
This site offers a daily HaniDoku with an archive of previous puzzles and solutions.
Check our freeware HaniCue program. You can play HaniDoku on your Windows PC with this unique program.
What is HaniDoku?
A Hanidoku puzzle looks like a honeycomb. It has hexagonal cells. Like in regular Sudoku, there are 9 rows, but there are no columns. Instead, there are lines that run in 60 degree angles from the horizontal rows. We call the ascending lines inclines and the descending lines declines. There are 9 of each type of line. The rows are numbered from top to bottom and the other lines are numbered from left to right. To be able to communicate about these lines, use this shorthand code: /3/ is the 3rd incline, \5\ is the 5th decline and =4= is row 4.
To identify cells in the grid, I advice you to use RnCn notation. R4C7 is the 7th cell in row 4, counting from left to right.
The lines have different lengths. Each line type comes in sizes 5-6-7-8-9-8-7-6-5. There is only one line for each type that has size 9, all shorter sizes appear twice.
The lines of length 9 must contain all digits 1 through 9. This rule is similar to the rule of Sudoku. However, the shorter lines must contain consecutive numbers. For example, =4= contains 8 cells. It can either contain digits 1 through 8 or digits 2 through 9. One of the new aspects of HaniDoku is that you do not know which of these two series is used. In your solving strategies, you must make a distinction between mandatory digits (2-8) and optional digits (1,9). A line of size 5 has many alternative series: 12345, 23456, 34567, 45678 or 56789. The only mandatory digit in such a line is 5.
The name HaniDoku stems from the Japanese word “hanikamu”, which is used for honeycomb. Take the shape of this puzzle, combine it with “sudoku”, and here is the entymology for this new word.
The most interesting part of this format are the lines in 3 directions, with different sizes. Here is a table that shows the possible digit series for each line size:
An optional digit can become mandatory in an individual puzzle, when more information becomes available when you solve it. There are different reasons that make an optional digit mandatory:
Optional digits can also be eliminated from a line. On a line of size 5, 6 or 7, you can find optional digits that require another optional digit to be present. For example, digit 9 requires digit 8 to be available, otherwise it cannot be used in a series. When digit 8 has no candidates left in a line, digit 9 can also be eliminated from the entire line.
You can save or print the worksheet page, to create worksheets that enable you to solve HaniDoku manually.