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## How to play

A Sudoku is a logic puzzle, there is no guessing involved, there is no maths involved, it is a pure logic puzzle.
This is an example of a starting grid for Sudoku - there is always some numbers that are given to you to start with. The more numbers you are given to start with, the easier the puzzle (normally).
There are three rules to Sudoku,
Each column must contain the numbers 1-9 once, and only once. The highlighted column already contains the numbers 5 and 7, you need to work out where the numbers 1, 2, 3, 4, 6, 8, and 9 need to go.
Each row must also contain the numbers 1-9 once, and only once. The highlighted row already contains the number 4, you need to work out where the numbers 1, 2, 3, 5, 6, 7, 8, and 9 need to go.
Each 3x3 region must contain the numbers 1-9 once, and only once. The highlighted 3x3 box already contains the numbers 2, 4, 6, and 7, you need to work out where the numbers 1, 3, 5, 8, and 9 need to go.
The easiest way to start is to look for cells where there is only one possible candidate. We know the bottom-left 3x3 region must contain the number 5 somewhere, but we don't know where. We also know that each row and column can only contain the number 5 once. This means we can eliminate all of the cells in that bottom-left square, apart from one. We can write in a '5' for the highlighted square.
This is a great technique to start with Sudoku puzzles.
The highlighted cell is another cell that we can fill right away. We can look at the numbers already in that column, row and 3x3 region, and by a process of elimination, work out what the highlighted cell should be.
That column already contains 2, 3, 4, 6 and 7. That row already contains 5, 6 and 8. That 3x3 region already contains 6 and 9. We know the highlighted cell can't be any of these numbers, because we can only have one of each number in each column, row, and 3x3 region. The highlighted cell can't be any of 2, 3, 4, 5, 6, 7, or 9. This leaves us with just the number 1!
I have highlighted three squares that you can fill in using the two techniques you have just learnt.
The rest of the puzzle can be solved using the two techniques you have just learnt.
All of our puzzles are graded easy, medium or hard. Go to the archive page and find an easy puzzle to start with!
This page will automatically load the puzzle for today. If you want to play a different puzzle, go to the archive page and choose your puzzle.
There are two ways to play a Sudoku puzzle, you can just use the mouse/touchscreen, or you can use the mouse and keyboard. You can switch between the two methods any time you like, and can use a combination of both.

### Playing with a mouse/touchscreen.

• When you have found a square where you can enter a number, click/touch that square. The square will turn light blue.
Above and below the puzzle is the number selection. Click/touch the number you want to enter in to that cell. If there is already a number in that square, it will be over-written.
• If you want to enter a pencil mark, click/touch the square you want to put in a pencil mark. It will turn light blue. Click/touch the pencil icon above or below the puzzle. This icon will turn light blue, and you are now in pencil marks mode.
Whenever you click/touch a number now, a pencil mark will be put in the square instead. To remove a number as a pencil mark, make sure you are in pencil marks mode, and click/touch the number again.
You can exit pencil mark mode by clicking/touching the pencil icon, it will turn back to normal.
• If you want to clear a particular square, make sure that square is selected and is in light blue. Click/touch the eraser icon. If there is a number in that square, it will be removed. If you click/touch it again, any pencil marks in that square will be removed.

### Playing with a mouse and keyboard.

• You will need to select a square by clicking on it with the mouse, it will turn light blue. You can change the current square by using the cursor keys on your keyboard.
• To enter a number, press that number on the keyboard. If there is already a number in that square, it will be overwritten. To remove a number, press the backspace or delete key on your keyboard.
• To enter a pencil mark, press control, shift, or alt on your keyboard at the same time as pressing a number key. Do the same thing again to remove that pencil mark.
Any mistakes you make will be hilighted in red. The website will know when you have completed a puzzle and will tell you. If you have an account and are logged in, the website will remember that you have completed that puzzle. You will also take part in out leaderboards. It's free to create an account!