Sudoku can take on many different variant forms. The one main standard is that each of the numbers in a region needs to be unique. With so many different variations of the puzzle to choose from you will never run out of challenges. Start out slowly with the standard grid layout of 9 x 9 before you move on to one of the many variations that you can find. Your goal should be to solve the Sudoku puzzle with little “givens” as you can.

## Variants

Sudoku is usually played as a 9 x 9 grid which contains 3 x 3 regions. Although this is the most common grid layout there are many variations which can be found. The following grid layouts are not uncommon and can add an even more challenging level to the puzzle:

- 4 x 4 grid with 2 x 2 regions

- 5 x 5 grid with pentomino regions (these puzzles are

known as “Logi-5”)- 6 x 6 grid with 2 x 3 regions (grid used in the World

- 7 x 7 grid with six heptomino regions as well as a

- 9 x 9 grid that generally has nonomino regions

Larger grid puzzles are possible, such as the 16 x 16 grid layout published by Dell that is known as “Number Place Challenger”. As well, Nikoli in Japan as published a 25 x 25 grid. Yet another variant for the Sudoku puzzle is the for the numbers in the main diagonal areas to be completely unique.

Yet another variation of the Sudoku puzzle is “Gattai 5 Sudoku”. In this puzzle variation there are five 9 x 9 grids which overlap at the corner regions into the refined shape of a quincunx. In the New York Times this puzzles is known as “Samurai Su Doku”.

A popular Sudoku puzzle in 2005 was a three dimensional grid. This grid variation was invented by Dion Church and was first published in the Daily Telegraph. It became a

fast hit among those puzzlers who wanted the ultimate in puzzle action.

There have been alphabetical variants of Sudoku where letters replace the numbers. This type of a puzzle is sometimes called “Godoku” and can be very difficult to solve if there are few “givens” available. Alphabetical Sudokus are also known as “Wordoku”. The letters

required for the puzzle will be given to you beneath the puzzle. After you have arranged the letters they will spell out a word that lines up between the top left bottom and left corners of the grid. This little twist adds a completely different dimension to the puzzle. There will be times when you can guess the word and this will aid you in solving the rest of the puzzle by filling in the rest of the regions.

## Japanese Variants

There are many Japanese variations of Sudoku which appear in magazines all over the country. Each variation has its own challenges that attract different individuals.

Following is a list of the some of the Japanese variants which have been developed:

**Puzzles that are sequentially connected**: Sequential puzzles have you solving several 9 x 9 grid Sudoku puzzles at one time. The first puzzle has enough“givens” in it so that it can be solved on its own.

After you have solved the first puzzle some of the numbers are moved from the first solved grid to the grid of the second 9 x 9 puzzle. You will have to work back and forth from one puzzle to the other to successfully solve these sequential Sudoku puzzles.

**Overlapping puzzles**: One popular version of Sudoku are multiple overlapping puzzles. These large puzzles are made up mostly of 9 x 9 grids but often these grids deviate from the standard. It is not uncommon to have one puzzle made up of 20 to 50standard 9 x 9 grids. Regions of each puzzle will overlap with one another. For instance, two 9 x 9 grids may have 9, 18, or 36 cells that are in common with each other. And other times there may no overlapping areas at all to connect with one another.

**Multiple cells**: This variation of the Sudoku puzzle appears quite simple at first. Each cell in a 9 x 9standard puzzle is part of four other puzzles rather than just the standard three parts – rows, columns, and regions. In this case numbers that are located within their region area can not match. This type of puzzle will usually be printed in color so that you can easily identify which area of the grid you are working on.

**“Digital Number Place”**: In 2005 the World Puzzle Championships include a puzzle of this kind, calling it “Digital Number Place”. Instead of being provided with a “given” most of the cells contained a partial given. A partial given is a segment of a number where some portions have been drawn as though they are part of a liquid crystal display. With so many Sudoku variations to choose from you will be able to spend hours and hours facing the challenge of solving them.

## Terminology and Rules

The Suduko puzzle is quite easy to solve, at least in the general concept. Your goal will be to fill in each of the empty cells with one number. Every row, column, and region will contain the numbers from one to nine exactly one time. This means that every number in the solution

of the puzzle will occur only one time in three directions.

The reason that so many people are attracted to a Sudoku puzzle is that, even though the solving rules are simple, the reasoning behind the path to the correct solution can be very difficult. Most puzzles will be ranked according to how difficult they are. Still other puzzles will give you an estimated time of how long it should take you to solve the puzzle. In most cases, the more “givens”

there are, the easier the puzzle will be to solve. The bottom line on how easy it is to solve a Sudoku puzzle will depend on how easy it is to determine the logical order of all of the numbers.

Many teachers, no matter what age range they are teaching, recommend Sudoku as a great way to develop logical reasoning. The complexity of each puzzle can be adapted to fit any age.