Sudoku
Sudoku: Quick Guide and Game Info
Sudoku is a logic puzzle played on a 9×9 grid. Your goal is to fill every empty square with a number from 1 to 9 so that each number appears exactly once in every row, column and 3×3 box.
In our version, you can choose between Easy, Medium and Hard puzzles. You have four mistakes available before the puzzle ends, along with three hints, a Notes mode for keeping track of possible numbers and a timer that records your best time for each difficulty. Choose a difficulty and solve the puzzle at your own pace, or challenge yourself to beat one of your previous best times.
About Our Sudoku
Every puzzle uses the classic 9×9 Sudoku grid, divided into nine smaller 3×3 boxes. Some numbers are already filled in when the puzzle begins, while the remaining cells must be solved using the information on the board. You can choose between Easy, Medium and Hard, and your best completion time is saved separately for each difficulty. You have four mistakes available during each puzzle. Enter a fifth incorrect number and the run is over. If you get stuck, you can use one of your three hints to help you continue. Notes mode lets you place small candidate numbers in empty cells without committing to an answer. As you solve more of the puzzle, you can gradually eliminate those candidates until the correct number becomes clear.
And while you play, Prof. Marty will be nearby to keep an eye on proceedings.
Game Layout and Setup
Sudoku is played on a 9×9 grid containing 81 cells. The board is divided into nine smaller 3×3 boxes. Some numbers are already filled in when a puzzle begins. These are your starting clues and cannot be changed.
Each puzzle includes:
- Easy, Medium or Hard difficulty
- Four allowed mistakes
- Three hints
- Notes mode
- A puzzle timer
- Personal best times for each difficulty
- Prof. Marty keeping an eye on proceedings
Select an empty cell and use the number buttons beneath the board to enter your answer. If you’re not ready to commit to a number, switch on Notes mode to record the possible candidates instead.
How to Play Sudoku
Every empty cell needs a number from 1 through 9, but there are three important rules you must follow.
Each Row Must Contain 1–9 Once
The same number cannot appear twice in a horizontal row. When the puzzle is complete, every row will contain all nine numbers.
Each Column Must Contain 1–9 Once
The same rule applies vertically. Every column must eventually contain the numbers 1 through 9 without any duplicates.
Each 3×3 Box Must Contain 1–9 Once
Each of the nine smaller boxes must also contain all nine numbers exactly once. You don’t need to guess which number comes next. Sudoku is about using the numbers already on the board to eliminate possibilities until you can determine where another number belongs. Select a cell, choose your number and continue working through the grid. If you’re unsure, use Notes mode to keep track of the numbers that could still fit.
Complete all 81 cells correctly before using up your four mistakes to solve the puzzle.
How to Solve Sudoku
Sudoku isn’t about beating an opponent. The challenge is to gradually eliminate possibilities until every empty cell has one correct answer.
Here are some useful techniques to get you started.
Start With Nearly Completed Areas
Look for rows, columns and 3×3 boxes that already contain plenty of numbers. If a row contains eight different numbers, for example, the missing ninth number is immediately determined. These obvious placements are usually the best place to begin because every number you add provides more information for the rest of the puzzle.
Scan Rows, Columns and Boxes Together
Don’t look at an empty cell in isolation. Suppose a 3×3 box is missing the number 7. Check the rows and columns passing through each empty cell in that box. Existing 7s elsewhere on the board may rule out several positions until only one possible square remains. This kind of cross-checking is one of the most useful Sudoku habits to develop.
Use Notes to Track Candidates
When a cell could contain several numbers, switch on Notes mode and record the possibilities. As you solve neighboring cells, some candidates become impossible and can be eliminated. Eventually, you may be left with only one possible number. Notes become particularly useful on Medium and Hard puzzles where the next answer isn’t always immediately obvious.
Look for Naked Singles
A naked single occurs when only one number can possibly fit in a particular cell. For example, if a cell’s row, column and 3×3 box already contain every possible number except 4, that cell must contain a 4. These are among the easiest opportunities to spot, so regularly scan the board for cells with only one remaining possibility.
More Sudoku Strategy Tips
Look for Hidden Singles
Sometimes a cell still has several possible candidates, but one particular number has only one possible location within a row, column or box. That’s known as a hidden single. Instead of concentrating only on individual cells, look across an entire row, column or box and ask where a particular missing number could actually go.
Use Naked Pairs
A naked pair occurs when two cells in the same row, column or 3×3 box contain exactly the same two candidates. For example, imagine two cells can each contain only 3 or 8. Those two numbers must eventually occupy those two cells in some order. That means 3 and 8 can be eliminated as possibilities from the other cells in that row, column or box. You may not immediately know which cell is 3 and which is 8, but you’ve still learned something useful about the rest of the puzzle.
When You Get Stuck
If nothing seems obvious, don’t immediately start guessing. Go back over your Notes and check whether a number you’ve recently placed eliminates any old candidates. Look again at nearly completed rows, columns and boxes. One new number can sometimes create several opportunities elsewhere on the board.
More advanced Sudoku techniques exist, including patterns such as X-Wings, but you won’t necessarily need one just because you’re playing a Hard puzzle.
And remember: our version gives you three hints. There’s no shame in asking for a little help when the grid refuses to cooperate.
Professor Marty
Marty has apparently acquired a professorship since his appearances elsewhere on Evergreen Arcade.
Prof. Marty hangs out beside the Sudoku board and reacts while you work your way through the puzzle.
He won’t solve the grid for you, that’s what the Hint button is for, but he’ll be there to keep you company while you figure things out.
Whether his academic credentials are legitimate remains under investigation.
A Little Bit of Sudoku History
Despite its Japanese name, the modern Sudoku puzzle has important American roots. In 1979, Dell Pencil Puzzles and Word Games published a puzzle called Number Place, generally credited to retired architect Howard Garns. It used the familiar idea of placing numbers in a 9×9 grid without repeating them across rows, columns and 3×3 boxes.
The puzzle later became popular in Japan after being introduced by puzzle publisher Nikoli during the 1980s. Its Japanese name was eventually shortened to Sudoku, based on a phrase referring to numbers appearing only once. Sudoku’s international popularity exploded during the 2000s as newspapers around the world began publishing the puzzles regularly.
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