Fill in the grid so that every row, every column, and every 3 x 3 box contains the digits 1 through 9. For each cell with a circle sum of its vertical neighbours must be equal to the sum of its horizontal neighbours.

Fill in the grid so that every row, every column, and every 3 x 3 box contains the digits 1 through 9. The sums of the digits within each sub-region are equal to each other. In sub-regions there can't be the same digit repeated.

Fill in the grid so that every row, every column, and every 3 x 3 box contains the digits 1 through 9. The sums of the digits within each sub-region are equal to each other. In sub-regions there can be the same digit repeated.

Fill in the grid so that every row, every column, and every 3 x 3 box contains the digits 1 through 9. The relation signs mark the relations between the sums of the digits of the sub-regions.

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 will have exactly one of each digit. The clues along the edges tell you how many skyscrapers you can see from that vantage point.

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

- Upper left - Even/Odd Sudoku: Yellow cells must contain odd digits, green cells must contain even digits.
- Upper centre - Min Max Quad Sudoku: The red points in the near of crosses where four cells meet each other show that the cell with the red points is greater then the three other ones. The blue rings in the near of crosses where four cells meet each other show that the cell with the blue ring is smaller then the three other ones.
- Upper right - Arrow Sudoku: The digit in the circle is the sum of the digits which are marked with its arrow.
- Centre left - Difference Sudoku: The numbers between two cells give the difference of the digits.
- Centre - Navigator Sudoku: The arrows show the location of the same number in the previous or next column or row. So for example, the arrow in fifth column means that the same digit is in the sixth column in row 6 - 9.
- Centre right - Greater/Less Sudoku: The inequality between each pair of digits must stand correct.

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 digit in a circle is the sum of the digits which are marked with its arrow.

Fill in the grid so that every row, every column, and every 2 x 3 box contains the digits 1 through 6. The digit in a circle is the sum of the digits which are marked with its arrow.

Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9. The sum of the connected pairs is 10.

Fill cages in the grid so that each cell is part of exactly one cage. Additional fill digits in the grid so that every row, every column, and every 3 x 3 box contains the digits 1 through 9. In every cage is exactly one number and this is the sum of the digits in this cage. All cages are rectangles or squares of at least two cells. In cages no number is repeated.

Example:

Puzzle: