Sudoku is played over a 9x9 grid, divided to 3x3 sub grids. Sudoku begins with some of the grid cells already filled with numbers. The object of Sudoku is to fill the other empty cells with numbers between 1 and 9. Number can appear only once on each row, and number can appear only once on each column. Also,number can appear only once on each 3x3 sub grids. The difficulty can be selected by three stages. 数独是打出过9x9的网格，分为3x3的分格。 数独开始与一些已经写满数字的网格单元。 独的目的是填补其它空细胞用1和9之间的数字。 数可以在每个行中只出现一次，并且数量可在每列仅出现一次。 此外，数字只能出现在每个3x3的分格一次。 困难可以通过三个阶段来选择。