# X SUDOKU

X-Sudoku is a variant of the classic Sudoku, in which two additional diagonals on the playing field can only contain each number exactly once.

This additional opportunity to exclude possible solutions creates a new challenge for the brain.

# X diagonals

The eponymous diagonals are highlighted by a colored background. In the example of a 9x9 X-Sudoku board, they are also 9 fields long.

# X diagonals

The eponymous diagonals are highlighted by a colored background. In the example of a 9x9 X-Sudoku board, they are also 9 fields long.

# Pairs

In Sudoku the term pair is used when there are only two possibilities for a number in a box left and they are on the same row or column - or in the case of an X-Sudoku on the same diagonal. If such a pair is known, it excludes the corresponding number for all other cells in the same column, row, or diagonal.

# Pairs

In Sudoku the term pair is used when there are only two possibilities for a number in a box left and they are on the same row or column - or in the case of an X-Sudoku on the same diagonal. If such a pair is known, it excludes the corresponding number for all other cells in the same column, row, or diagonal.

# Boxes, Columns, Rows, and Cells

All other elements of an X-Sudoku correspond to those of the classic Sudoku. You can find an explanation of these terms in the game instructions for Classic Sudokus.

# Boxes, Columns, Rows, and Cells

All other elements of an X-Sudoku correspond to those of the classic Sudoku. You can find an explanation of these terms in the game instructions for Classic Sudokus.

# Rules

A Sudoku puzzle can be solved by applying the basic rules of Sudoku. These say that in a 9x9 Sudoku, each number from 1 to 9 can only appear once in each column, each row and each box. If a number has already been revealed or is given, it is excluded from all other cells in this row, column or box.

In X-Sudoku, this rule also applies to the two highlighted diagonals. These may also contain each number from 1 to 9 only once. This also creates dependencies between the boxes along the diagonal, which do not exist in classic Sudoku and can help the player solve the Sudoku.

In the example, the marked four for the box in the middle can also be used for F4 can be excluded because it has already been revealed on this diagonal.

A Sudoku puzzle can be solved by applying the basic rules of Sudoku. These say that in a 9x9 Sudoku, each number from 1 to 9 can only appear once in each column, each row and each box. If a number has already been revealed or is given, it is excluded from all other cells in this row, column or box.

In X-Sudoku, this rule also applies to the two highlighted diagonals. These may also contain each number from 1 to 9 only once. This also creates dependencies between the boxes along the diagonal, which do not exist in classic Sudoku and can help the player solve the Sudoku.

In the example, the marked four for the box in the middle can also be used for F4 can be excluded because it has already been revealed on this diagonal.

# Step 1

On this 9x9 X-Sudoku we can use the diagonals to solve the Sudoku. In this game guide we will therefore focus on the special features that arise from the diagonals. In the Guide for Classic Sudoku you will also find information about other strategies.

# Step 1

On this 9x9 X-Sudoku we can use the diagonals to solve the Sudoku. In this game guide we will therefore focus on the special features that arise from the diagonals. In the Guide for Classic Sudoku you will also find information about other strategies.

# Step 2

Let's first look at the already given 8 in cell D6. This lies on the diagonal from top right to bottom left. This allows us to exclude the 8 in the box at the bottom left of all cells on this diagonal.

# Step 2

Let's first look at the already given 8 in cell D6. This lies on the diagonal from top right to bottom left. This allows us to exclude the 8 in the box at the bottom left of all cells on this diagonal.

# Step 3

This leaves only two options for the 8 in this box at A7 and B7. The resulting pair on a row excludes the 8 for all other cells on row 7. This leaves only one option to enter the 8 in the box at the bottom center. This is in cell E8.

All other cells are blocked by other eights. The same applies to the 8 in H4.

# Step 3

This leaves only two options for the 8 in this box at A7 and B7. The resulting pair on a row excludes the 8 for all other cells on row 7. This leaves only one option to enter the 8 in the box at the bottom center. This is in cell E8.

All other cells are blocked by other eights. The same applies to the 8 in H4.

# Step 4

On the same diagonal we find a 2 in cell F4. This prevents the possible 2 in cell H2 from the box at the top right. This allows us to enter the 2 as a pair in this box and reveal the 2 in cell E2.

Other twos can also be solved using the last options at I6 and E2.

# Step 4

On the same diagonal we find a 2 in cell F4. This prevents the possible 2 in cell H2 from the box at the top right. This allows us to enter the 2 as a pair in this box and reveal the 2 in cell E2.

Other twos can also be solved using the last options at I6 and E2.

# Step 5

Using the 3 in cell H8 on the diagonal from bottom right to top left, we can reduce the 3 in the middle box to two possibilities. These are cells D5 and F5. This pair leaves only one possibility for the 3 in cell G6 in the middle right box.

# Step 5

Using the 3 in cell H8 on the diagonal from bottom right to top left, we can reduce the 3 in the middle box to two possibilities. These are cells D5 and F5. This pair leaves only one possibility for the 3 in cell G6 in the middle right box.

# Step 6

Using our revealed threes so far, we can also narrow down the 3 to a pair in the box at the top right. Because it is also in the top middle box, either in the bottom or top row of this box, we know that in the top left box it can only appear in the middle row and we can see it as a pair at A2 and C2 and note them down. With this strategy, previously hidden numbers can be narrowed down or revealed in many Sudokus.

# Step 6

Using our revealed threes so far, we can also narrow down the 3 to a pair in the box at the top right. Because it is also in the top middle box, either in the bottom or top row of this box, we know that in the top left box it can only appear in the middle row and we can see it as a pair at A2 and C2 and note them down. With this strategy, previously hidden numbers can be narrowed down or revealed in many Sudokus.

# Step 7

Now let's look at number 4. For it there is a pair in the cells G3 and I3 in the box at the top right. However, the 4 on this diagonal can only be entered in cell G3 because it is already revealed in the other two boxes crossed by this diagonal. With newly discovered 4 we can also reveal all other fours on the board.

# Step 7

Now let's look at number 4. For it there is a pair in the cells G3 and I3 in the box at the top right. However, the 4 on this diagonal can only be entered in cell G3 because it is already revealed in the other two boxes crossed by this diagonal. With newly discovered 4 we can also reveal all other fours on the board.

# Step 8

We have a similar situation for the 5. Since it is prevented for this diagonal in the top right box, it must therefore be found in the bottom left box. From an already given spark in cell G7 we know that the possibilities are reduced to cells B8 and A1 of this diagonal. Since we can also reveal the 5 in cell D9 as a last resort, only cell B8 remains. All other fives can also be revealed.

# Step 8

We have a similar situation for the 5. Since it is prevented for this diagonal in the top right box, it must therefore be found in the bottom left box. From an already given spark in cell G7 we know that the possibilities are reduced to cells B8 and A1 of this diagonal. Since we can also reveal the 5 in cell D9 as a last resort, only cell B8 remains. All other fives can also be revealed.

# Step 9

In the diagonal from top left to bottom right, the 6 is not yet revealed. Since it is prevented for cell F6, we can enter it in D4 and thus solve it for the box in the middle at the same time. This means we can completely uncover this diagonal by applying the rule that every number from 1 to 9 must appear exactly once in each diagonal. This allows us to reveal the number 7 at F6.

# Step 9

In the diagonal from top left to bottom right, the 6 is not yet revealed. Since it is prevented for cell F6, we can enter it in D4 and thus solve it for the box in the middle at the same time. This means we can completely uncover this diagonal by applying the rule that every number from 1 to 9 must appear exactly once in each diagonal. This allows us to reveal the number 7 at F6.

# Step 10

Even if the 9 has only been revealed three times on the playing field as a default, we can already solve it one more time for the Diagoanle. The 9 for the diagonal cannot be entered in the box at the top right. This leaves the box at the bottom left as the only option. There the 9 for the diagonal is blocked by a default at in column C and we only have one last chance to reveal it at A9. This leaves only one option for all other cells of the nine and we have revealed all nines.

# Step 10

Even if the 9 has only been revealed three times on the playing field as a default, we can already solve it one more time for the Diagoanle. The 9 for the diagonal cannot be entered in the box at the top right. This leaves the box at the bottom left as the only option. There the 9 for the diagonal is blocked by a default at in column C and we only have one last chance to reveal it at A9. This leaves only one option for all other cells of the nine and we have revealed all nines.

Step 11

We can also uncover additional cells using the numbers we have already solved. To finally solve the three, the diagonal helps us again. Because although a pair of the three in row 7 remains open for the box at the bottom left, we can enter the 3 in cell C7. We know this because it can only be here for this diagonal - in the top right box it is prevented by the revealed 3 in cell I3.

Step 11

We can also uncover additional cells using the numbers we have already solved. To finally solve the three, the diagonal helps us again. Because although a pair of the three in row 7 remains open for the box at the bottom left, we can enter the 3 in cell C7. We know this because it can only be here for this diagonal - in the top right box it is prevented by the revealed 3 in cell I3.

# Step 12

With this and the other cells already solved, we can also reveal the last two numbers of the diagonal. In cell I1 we find a 6 and in cell H2 the last possibility of this diagonal is 7.

# Step 12

With this and the other cells already solved, we can also reveal the last two numbers of the diagonal. In cell I1 we find a 6 and in cell H2 the last possibility of this diagonal is 7.

# Step 13

Now we are able to finally solve this X-Sudoku. All other numbers that are still hidden only have one possibility. With the last 6 we conclude this Sudoku.

# Step 13

Now we are able to finally solve this X-Sudoku. All other numbers that are still hidden only have one possibility. With the last 6 we conclude this Sudoku.