Free Online Sudoku Puzzle
The rules to play Sudoku are very simple. Fill in the blanks so that each row, each column, and each of the nine 3x3 grids contain one instance of each of the numbers 1 through 9. In this online version there are four levels of difficulty. When playing the game, to enter a number, click on an empty cell, then choose the number you want. Annotations can be added to each cell by using the the Pencil Marks feature. Puzzles can be printed for solving them on paper instead of online.