The game is played on a grid of 9 x 9 cells, 81 cells, which in turn is divided into 3×3 sub-cells , which are also known as “boxes” or “regions”. The object of the game is to complete with numbers from 1 to 9, based on a series of numbers prepared in some of the cells.
Colors, letters or figures could be used, but numbers are in use because they are easier to memorize.
A number should not be repeated in the same row, column or sub-cell. It is said that a game has been raised whether there is only one solution.

Generally sudokus that are published in newspapers or on the online versions, are classified according to

difficulty. While to the surprise of many, the amount of numbers given hardly affects the difficulty of

sudoku. A game with the minimum number given can be resolved quite easily, though one with more

numbers given may be quite difficult to resolve. This is because the game is based on the relevance and

positioning of numbers, rather than quantity.
To offer various difficulties involved, there are computer programs that can estimate how difficult it meant

for one person to find a solution, based on the techniques necessary resolution. With these estimates is possible to provide different levels of difficulty, especially in the online version of sudoku, which offer

various levels of play.