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What Is Sudoku66?

Sudoku66 makes it possible to play Sudoku at any time online using your cell phone, tablet, or computer. Our website is available 24/7 – no registration required. Best of all, Sudoku66 is completely free to play. Whether you are an experienced Sudoku player or you have never played Sudoku before, you will love Sudoku66!

Sudoku Rules – Explained in Simple Terms

The name Sudoku comes from Japan and consists of the characters „Su“ (engl. „number“) and „Doku“ (a single place on the puzzle board that each number can fit into). The objective of the game is to fill the grid so that each row, column and each of the 9 boxes (also called 'regions' or 'blocks') contains the digits from 1 to 9 within its squares. Each row, region and column consists of 9 cells. Does it sound complicated?

As you can see easily when you start playing Sudoku66, each Sudoku grid comes with a few spaces already filled in. Sudoku puzzles with easy difficulty have lots of cells that are filled in. Difficult Sudoku boards require more complex logic as they have very few filled in spaces. Click the question mark symbol at any time to get an overview of the Sudoku rules.

How to Play Sudoku with Sudoku66

To play Sudoku on sudoku66.com, just open the website and hit the „Start“ button. In the next screen, click on the „Play“ button to start the game. You can turn off the sound effects by clicking the speaker icon in the upper right corner. There are 3 different levels of play: Beginner, Intermediate and Advanced.

The board screen shows a standard Sudoku board with 81 cells. Below the board, you find the digits 1 to 9. The aim is to complete the grid so that each line, both vertical and horizontal, contains every digit in the set. You can abort the game at any time by clicking the „X“ button in the upper right corner. To undo your last action, click the „X“ symbol in the lower bar of the board.

Sudoku66 – Features

By clicking the gear symbol, you are directed to a menu page that shows the following options:

If you play Sudoku66 on a notebook or desktop computer in full screen mode, press the Escape button to switch back to normal view. Hitting the „Reset“ button sets everything back to start.

Sudoku66 – Game Modes

Sudoku66 offers 3 different game modes (cell first mode, numbers first mode and memo mode). While the memo mode allows you to write down a memo in a blank, the cell first mode allows you to fill in your chosen cell first and to select the digit you want to enter afterwards. In numbers first mode, select the number you want to enter first and then click the cell you want to fill in.

Keep in mind that each number can appear only once in a row, column or box. Every Sudoku puzzle has only one correct solution.

Hidden Pairs and Triples

In Sudoku, a „Hidden Pair“ is basically a buried „Naked Pair“. A Hidden Pair occurs when two pencil marks show up in exactly two cells within the same house (block, column, or row). Hidden Triples work in a similar way as Hidden Pairs. The only difference is that there are three cells and three candidates.

Looking for Hidden Pairs (or „Hidden Candidates“) is a great way to open up the board. This popular approach can eliminate a cluster of candidates from two cells, so that only simple pairs are left behind. Simple pairs are the building blocks of more sophisticated elimination strategies.

Don’t Guess!

Sudoku is known as a game of reasoning and logic – therefore, you shouldn't have a guess. The only time you would need a guess is when a puzzle is improper and thus has more than one possible solution. However, this case will never arise in our gaming solution.

If you do not know which number to fill in a certain box, keep searching the other areas until you spot an opportunity to place a number. Sudoku rewards patience and recognition of patterns, not guessing or blind luck – so don’t try to „force“ anything.

Sudoku66 Can Be Played Anywhere

Sudoku66 is available on almost every device. You can play it in moments of downtime – for example during your coffee break, at home or in the office. If you commute by bus or train, you can play Sudoku66 on your way to your workplace. Some people even play Sudoku while they are aboard an airplane.

The easy portability is one reason why Sudoku became so popular in Japan. For Japanese people, it is very common to have long train rides to work every day. Japanese women and men alike love to pass the time with Sudoku puzzles.

How Sudoku66 Can Improve Your Health

One of the reasons why Sudoku is so popular nowadays is that it can be used to exercise the brain. Studies show that keeping your brain active reduces the chances of developing mind-altering diseases like dementia or Alzheimer's. Sudoku66 stimulates your mind and improves your number skills. It requires you to think strategically and to solve problems creatively.

While there is no guarantee that playing Sudoku protects you against mental illnesses, the game can help you to stay mentally sharp and healthy. By playing it more often, you can solve the puzzles faster and better each time. Sudoku also gives you a great sense of accomplishment and completion. There is something very fulfilling and satisfying about solving Sudoku puzzles and gradually working your way to the end.