If you prefer to enter your own pencilmarks, up to six digits can be entered in each cell. You can add symbols too, such as question marks. If you like playing some seriously hard Sudoku, try the puzzles at the end of The Times Sudoku 6 book with some requiring the swordfish technique. While it's totally fine to play sudoku intuitively on the easy levels, evil sudoku requires the knowledge of some strategies. Here is the most popular one for solving sudoku on the evil level.

This hardest Sudoku puzzle is characterized by the fact that only a few numbers are shown in the Sudoku square, which consists of 9 small squares, where the cells are located 3x3. Sudoku Rules Extreme Sudoku posts five new puzzles every day. Each puzzle has a unique solution and can be solved with pure logic. Lots of it. Guessing is never required - but it may help! If you really like Super Fiendish, you will have to wait a little longer for The Times Sudoku 7 with 25 extremely hard Sudoku, many requiring x-wing or swordfish to complete. Sudoku.com has some features that will help you with expert level Sudoku. An option that is especially useful at the beginning of the game is the ability to select a hint. The correction function is also very useful, since due to the high level of complexity, it is necessary to make corrections more often.

Blackjack Strategy

Essentially, this method uses the fact that in certain cases, there are only two possible ways of placing two numbers in four squares which form a rectangle.

submissions and try for the Experts list. Anyone can get into the Top Sudoku Expert list - this is now the sum of all your correct entries for the In this case, this particular number can be eliminated as a possibility for all other squares in those two columns. In general, an x-wing is found when for two rows, there are two, and only two, possible squares in which a particular number can be placed, and for both rows these squares lie in the same two columns. It is a fact that you cannot place the 7 in the first column square of both the highlighted rows at the same time.If lines are drawn along the rows and columns, connecting the squares involved, they can form two rectangles, connected at the corners. So, there are two possible ways of placing the 7; how does this help you solve anything? Well, you have established that the 7 for the first column must be in one of the two highlighted rows; not in any other squares in this column. Therefore, on each of the three intersecting rows, the 3 must be placed in one of the highlighted columns. Sudoku is one of the world’s most popular puzzle games, but even though it’s a game played by millions of people all over the world, there is a big difference in skill level between the most successful Sudoku players and average Sudoku players who enjoy the game just as a casual hobby. Using the same logic in the last column, you can also eliminate the 7 as a possibility from all squares which are not in either highlighted row (Fig. 2).