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. Each row, column, 3x3-box and diagonal will have exactly one of each digit. In green cells can only be even digits. In yellow cells can only be odd digits. If two orthogonally or diagonally cells are connected with a red line then the numbers in these cells are consecutive.

Fill the grid with the digits 1 to 9. Each row, column and 3x3-box will have exactly one of each digit. In green cells can only be even digits. In white cells both odd and even digits are possible.

Fill the grid with the digits 1 to 9. Each row, column and 3x3-box will have exactly one of each digit. In yellow cells can only be odd digits. In white cells both odd and even digits are possible.

Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9. Yellow cells must contain odd digits, green cells must contain even digits.

Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9. Yellow cells must contain odd digits, green cells must contain even digits.