# Play Free Sudoku online

Sudoku is a game that works on improving logical thinking but doesn’t require you to solve complex mathematical operations. It was first created in Japan. As you gradually gain more experience with this puzzle, you’ll be able to develop your concentration, patience, and thinking skills. You will also learn how to build logical chains of inferences.

At the beginning of the game, you will see a grid of 81 cells, which are split up into 9 sectors. Each sector has the dimension of 3 by 3 cells (9 cells in each sector). In some cells, there will be a number ranging from 1-9. The player must fill in the remaining empty cells, according to the numbers given.

## The goal of the game

The goal is to arrange numbers 1,2, 3, 4, 5, 6, 7, 8, and 9 in the empty cells in such a way that every sector, every column, and every row contains the numbers 1-9 only once.

## How to play?

Click on the cell that you need and press the necessary button (1, 2 … 9) on your keyboard’s number panel. The puzzle is considered completed as soon as you fill in all the cells correctly.

Keep in mind, that there cannot be any repeated numbers in one row (1 by 9 cells), column (1 by 9 cells), or sector (3 by 3 cells).

## Strategies

For quick and successful puzzle completion, you can refer to the strategic recommendations below:

- Find the 3 by 3 sectors which already contain 5 or more numbers. Using logic and the other numbers in the rows and columns, try to quickly fill in the missing numbers. The more sectors you can finish, the more obvious will be your further steps for completing the puzzle.
- The board can be visually divided into 3 rows and 3 columns, where each row and column contains 3 sectors. If in any such row or column there are two sectors with two of the same numbers, then in the third sector there will also be the same number. For example, in the first one of these rows, we see the number 1 in the left and middle sector. This means that 1 will also be in the right sector of this row.

## Game interface

In order to make the game process convenient for all users, we have created an interface with special functional abilities:

- «New game» button. Pushing this button will open a popup menu with three choices: «New game» (to generate a new combination of numbers on the game board), «Restart» (to return to the starting point of the current puzzle), and «Cancel» (to close the popup menu);
- Buttons «1», «2» … «3». Pressing one of these buttons after selecting a cell on the game board will fill in the cell with the corresponding number.
- «Erase» button. Pressing this button after selecting a cell that contains a number will delete this number, if it was filled in by the user.
- «Hint» button. Pressing this button will make some numbers appear in the cells where they could logically be located.
- «Cancel» button. Pressing this button allows you to cancel the previous steps one by one.
- «Notes» button. If this function is turned «ON», it allows to fill in more than one possible solution for each cell.
- «Check for errors» option. If this option is on, incorrect solutions will be highlighted in red.
- «Difficulty» option (difficulty level). There are several Sudoku difficulty levels for each user. The most difficult level contains the smallest amount of preset numbers in the beginning of the game.
- «Pause» or «Play» buttons (stop or continue). These buttons are located next to the timer. Pressing «Pause» will pause the game, and pressing «Play» will let you continue playing and arranging the numbers.