Basic Sudoku: Sudoku is played on a 9x9 grid which is divided in 3x3 small grids called regions. You have to fill each cell with one of the numbers from 1 to 9. Each column, row, and 3x3 box should have a complete series of numbers from 1 through 9 without any repetition. To place a number, simply use your mouse to click on a cell and choose from the available numbers.