Sudoku is the popular Japanese numbers game that came into Japan in 1986 and has now attained world-wide popularity. Sudoku means "solitary number" and is easy to learn yet provides a surprisingly wide variety of logic problems and challenges. The rules to Sudoku are very simple: fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9. Use the Hint button if you get really stuck. Select the square you need help on and click "Use Hint" to fill in the correct digit. You get up to 3 hints per level. There are 75 levels in total split up into the categories of Easy (1-25), Medium (26-50) and Hard (51-75). See if you can complete all the levels! There is a timer, but no time limit so you can play at your own leisure or put yourself under pressure and challenge your friends. You can use the keyboard to select squares using the Arrow Keys and then type in the digit you want to place. 0 will set the square to empty. Or you can simply fill in the grid by selecting squares with the Mouse and pick digits from the small grid that pops up.