Code Sudoku Rulebook

Table of Contents

Table of Contents

• Contents
• Assembly
• Rules of the Game
  • Tips
• Techniques
  • 1. Visualisation techniques
  • 2. Analysis techniques
• Multiplayer Game
  • Tip

Contents

• 48 number grids in 4 difficulty levels
• A rules sheet and tips for improving
• The solutions to the 48 grids
• A two-part game board that allows the grids to be reused indefinitely
• 81 numbered tiles
• 8 "score" markers
• 1 erasable marker
• 1 sponge

Assembly

1. Place a number grid on the black board.
2. Place the transparent grid over it.
3. Insert the two tabs of the transparent grid into the slots of the black board.
4. Press lightly on it, following the arrows, so that it snaps into the board.

Rules of the Game

The rules of Sudoku are very simple, but the game demands patience, reflection and a great deal of logic.

The aim of the game is for each of the digits 1 to 9 to appear exactly once in each row, each column and each cell of the grid.

Grid Sudoku / Solution (the sheet shows a puzzle grid and its solution side by side).

Tips

• Use only a washable (erasable) marker.
• The 9 digits are written small in each square to be deciphered, to help progress in the game. Circle the digits that may fit and cross out the others.
• When only one circled digit remains in a square, place the matching numbered tile on that square.
• Start with the easiest grids, then increase the difficulty level gradually.
• Do not try to guess. Always proceed by elimination.
• Refer to the "Techniques" chapter to learn new tricks for progressing further.
• Remember that each grid has only one solution.

Techniques

The Code Sudoku™ board comprises 81 squares. It is divided into 9 columns, marked "a" to "i", and 9 rows, marked "1" to "9". The grid is divided into 9 cells (each containing 3 x 3 squares); see the diagram opposite. (The diagram labels the cells "Blok 1" to "Blok 9".)

1. Visualisation techniques

The best way to start is to scan and visualise each of the columns, rows and cells of the grid. This makes it possible to cross out every digit that cannot fit and circle the others. By elimination, it is then possible to decipher one or more squares where only one digit can fit. This technique is, as a general rule, the fastest and most effective way to decipher simple grids. It is also essential for starting the more complex grids, until it is no longer sufficient to decipher every square. At that point new methods are needed. Here are some examples of extensions of the visualisation technique:

A. Visualisation in one direction

In this example, focus on cell 2 which, like every cell, must contain the digit 9. Cells 1 and 3 already contain a 9, located on rows 2 and 3. The 9 of cell 2 therefore cannot lie on rows 2 and 3. Square "e1" is consequently the only possibility.

B. Visualisation in two directions

Try to find the place of the digit 1 in cell 3. In this example, the digit 1 is already present on rows 1 and 2. Only two possibilities remain, on row 3 within cell 3. A scan both horizontally and vertically shows that the digit 1 cannot be in square "4g", which already contains the digit 1. It must therefore be in square "3i".

C. Looking for the missing digit

It is frequent that only one digit can fit in a square because all the other digits are already part of the row, column or cell. Try to decipher square "4b". The digits 3, 4, 7 and 8 are already part of the cell. The digits 1 and 6 are already present on row "4", and the digits 5 and 9 on column "b". All the listed digits are therefore eliminated except the digit 2, which fits square "4b".

D. Eliminating by rows, columns and cells

In this example, the digit 1 is in square "8c". In cell 8, the 1 can only be in square "7e" or "9e". In either case, the 1 of column "e" can only be in cell 8. The 1 of cell 2 cannot be in column "e", so it is in square "2h".

E. Looking for the digit absent from a column and a row

This technique applies when a column or a row is almost completely deciphered. Look at row 6. Only the digits 6 and 7 are missing from this row. The 6 cannot go in square "6h" since it is already present in column "h". The 6 must therefore be in square "6b". Only one place remains for the 7, in square "6h".

2. Analysis techniques

The higher the difficulty level, the more complicated the techniques needed. To decipher the most complex grids, it is important to bring forward all the possibilities by circling them, then to cross them out progressively with the erasable board. Here are some examples of using the analysis technique:

a. Highlighting two possibilities in a cell

In this example, the digits in red are those circled on the erasable board. The digits 4 and 9 are the only ones that can fit in squares "7c" and "8c". It is still impossible to say which digit goes in which square, but it is certain that these two digits belong to these two squares. Moreover, there is already a 6 in column "a", so the 6 of cell 7 must be in square "b9".

B. Highlighting two possibilities in a row and a column

In this grid, the digits 2 and 7 can only be in squares "9d" and "9f". It is still impossible to say which digit goes in which square, but it is certain that these two digits belong to these two squares. The missing digits on row 9 are therefore 1, 6 and 8. The 6 cannot be in square "9a" or "9i", so it is in square "9c".

C. Highlighting two hidden possibilities in a row and a column

Highlighting two possibilities is sometimes harder to achieve. On row 7, the digits 1 and 4 can only be placed in squares "7f" and "7g". This implies that squares "7f" and "7g" can only contain these two digits, and after deduction the digit 7 is inevitably in square "7d".

Multiplayer Game

For a multiplayer game, each player takes 2 "score" markers of the same colour from the 8 included and places them on the board (see the diagram opposite).

The first marker records the units digit and the second records the tens digit.

Each player has one minute to place as many numbered tiles as possible on the board.

A player earns 1 point each time they place a tile. If they place a tile that completes a row, a column or a cell, they earn 3 points.

For example: if a player places 2 numbered tiles on the board, then another that completes a row, they earn 5 points (two points for the first two tiles plus three points for the third).

If a player places an incorrect tile, they must remove it from the board and their turn ends. It is then the next player's turn. The point(s) the first player would have earned had the tile been correct are awarded to the player who noticed the error.

The player with the highest score wins the game.

Tip

Since it is easier to score points at the start of the game, it is preferable for each player to be able to start one game.

For example: with 4 players, it is preferable to play 4 games in which the player who starts is never the same.