Sudoku is a highly strategic game that can be pretty hard to grasp at first. But, once you learn how to play Sudoku, it's easy to get sucked into its challenging and addictive nature. The rules for Sudoku are standard across all difficulty levels, but it's important to pay attention to your ability level before playing so that you have a good time instead of a frustrating one. If you've never played Sudoku before, start with something easy and work your way up from there. You'll soon see why it's such a popular puzzle. There is a lot of debate on whether the rules of Sudoku are the same for all difficulty levels. Many novice players believe that the harder puzzles have different rules, while experienced players claim that the only difference is the number of squares that are filled in. To settle this debate, let’s take a look at the official Sudoku rules. • According to these rules, the only difference between easy, medium, and hard puzzles is the number of squares that are already filled in. This means that all of the other rules are still in effect, including the requirement that each row, column. There are a finite number of Sudoku grids. The number of grids is the same for all difficulty levels. However, the number of girds that are valid for each level is different. For instance, a 6x6 Sudoku grid has only 42 valid grids. A 9x9 Sudoku grid has 234 valid grids.