Fill in the grids so that every row, every column and 3x3 box contains the digits 1 through 9. The sum of the digits within each sub-region is equal to the specified number. There must be a one-to-one correspondence between both twins, i. e., in all positions with a certain digit in the first grid must be in the corresponding position in the second grid also always the same digit (possibly another as in the first grid).

Fill the grid with the digits 1 to 9. The digits represent the height of the skyscraper in each cell. Each row, column and 3x3-box has exactly one of each digit. The clues along the edges tell you how many skyscrapers you can see from that vantage point. The sum of two cells with a bold line between them is always the same, the so called magic number.

This is a combination of some sudoku variants.

Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9. The grid must fulfill the following rules:

- Sudoku X: The both main diagonals contain each the digits 1 through 9.
- Sum Search Sudoku: The equal signs mark the relations between the sums of the digits of the cages. In cages there can't be the same digit repeated.
- Arrow Sudoku: The digit in a circle is the sum of the digits which are marked with its arrow.
- Ratio Sudoku: The fractions between two cells give the ratio of the digits. For example 2/3 can stand for the following combinations of numbers in the adjazent cells: 2 - 3, 4 - 6, 6 - 9, 3 - 2, 6 - 4 and 9 - 6.
- Wheel Sudoku: The wheels in the grid contain each 4 values. These values will go in the cells the numbers are in. Doing this the wheels must be rotatated to the right position. (Not mirrored or changed the order of the digits.)

Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9. The colored extra-regions must contain each the digits 1 through 9.

In each 3x3 box their is a differet rule to follow:

- Upper left - Consecutive Sudoku: All neighbouring cells with consecutive digits have a colored border.
- Upper centre - Killer <=>: Relation signs represent the relation between the sums of the digits in the sub-regions.
- Upper right - Greater/Less Sudoku: The inequality between each pair of digits must stand correct.
- Centre left - Arrow Sudoku: The digit in a circle is the sum of the digits which are marked with its arrow.
- Centre - Magical square: the sum of any row, any column and both main diagonals in this area is always the same.
- Centre right - Product Sudoku: Digits in a sub-region multiply up to the specified number.
- Lower left - Addoku: Digits in the outside equal the sum of the three numbers of the corresponding row or column in the contigous box.
- Lower centre - Killer: Digits in a sub-region add up to the specified number.
- Lower right - Sum Box Sudoku: First two row of numbers add up to the number formed on the third row.

This combination variant was introduced by Cihan Altay at the 1st Sudoku World Championship.

Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9. The colored extra-regions must contain each the digits 1 through 9.

In each 3x3 box their is a differet rule to follow:

- Upper left - Digital Sudoku: Digits are in digital form, as given below.
- Upper centre - Even/Odd Sudoku: Yellow cells must contain odd digits, green cells must contain even digits.
- Upper right - Consecutive Sudoku: All neighbouring cells with consecutive digits have a colored border.
- Centre left - Sum Sudoku (Killer Sudoku): Digits in a sub-region add up to the specified number.
- Centre - Classical Sudoku: No special rule.
- Centre right - Pips Sudoku: Digits are given as pips, like on dominoes or dices, as given below.
- Lower left - Big/Small Sudoku: Red cells must contain small digits (1 - 4), blue cells must contain big digits (5 - 9).
- Lower centre - Greater/Less Sudoku: The inewquality between each pair of digits must stand correct.
- Lower right - Sum Box Sudoku: First two row of numbers add up to the number formed on the third row.

Fill in the grid so that every row, every column, every 3x3 box and both diagonals contains the digits 1 through 9. The algraic operations in the cells must be fullfilled.

Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9. Each clue-number is the product of the two neighbored digits.

Fill in the grid so that every row, every column, and every 3 x 3 box contains the digits 1 through 9. The specified numbers are equal to the product of there horizontally and vertically adjazent cells. (There is no extra constraint that they must be different.)

Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9. Some rows and columns have numbers. They represent the product of the two ends.

Fill in the grid so that every row, every column, and every 3 x 3 box contains the digits 1 through 9. Digits in the outside frame equal the product of the three numbers of the corresponding row or column in the contigious box.