A X-Sudoku is a variant of the normal classic Sudoku. For X-Sudokus additionally to the rules of the classic Sudoku the two diagonals may only contain the numbers one to nine only once. The application marks the diagonals for X-Sudokus with a light contrast (depending on the contrast setting). For printouts the diagonals are also highlighted. New X-Sudokus are created either by selecting the menu item "File|New|X-Sudoku" (empty X-Sudoku) or by selecting "Problem|Generate|X-Sudoku". For booklets it is also possible to define whether or not it should contain X-Sudokus.