Online Sudoku
Welcome to OnlineSudoku.Games. We offer you to dive into the magic of numbers and enjoy the largest collection of Sudoku.
Sudoku Game Rules
First of all, let's figure out what Sudoku means. Sudoku is a numerical puzzle with a square field of 9x9 cells inside, that is, 81 cells in total. Sudoku is also called a magic square. The square is divided into 9 small squares, 3x3 cells each like at the picture below.
At the beginning of the game, some cells has hints inside, the numbers from 1 to 9. The player's task is to fill the remaining empty cells with numbers from 1 to 9 so that the following three conditions are met:
- Numbers should not be repeated in one column;
- Numbers should not be repeated in one line;
- Numbers should not be repeated in a small square (3x3).
The difficulty of Sudoku depends on the initial number of hints. The more hints, the easier Sudoku is. Easy Sudoku can be solved in a few minutes. To solve a hard Sudoku, it may take more than an hour.
As a rule, Sudoku has one solution, but in complex Sudoku, a few options and solutions are possible. In our Sudoku such options are possible. As a result, the puzzle is considered solved if the entire square is filled and all three conditions are met.
Ways to solve Sudoku
There are a few methods to find solutions for Sudoku. We describe the two most popular of them.
Method of Intersections
In the method of intersections, the search is done by small squares. In every small square there must be one digit from 1 to 9 without repetitions. In Sudoku, there are three small horizontal squares and three vertical ones. For an example, let’s begin the search with the number 1. We know that there must be only one number 1 in every small square. Let’s look for a small square with no digit 3. Then, let’s look for number 3 in the adjacent small squares in this column and row. Let’s exclude columns and rows where figure 3 occurs in adjacent small squares and try to establish the position of the digit 3 in the original small square. In the figure, we showed the search for number 3 and found the right place using the method of intersections.
Let’s continue to search for other digits and find the right spots for them.
It's very easy to use this method in our game. You have to click on any digit in the box. This number will be highlighted in all small squares and you will easily find the right place in a small square where it does not yet exist.
After you tried all the options, you can check the next method.
Method of Exclusions
Let’s find an empty square and check the missing numbers in a small square, placed horizontally and vertically. There might be single solution with just one number. In this case, we write the number into a square and continue to look for solutions for other empty squares.
In case there are 2 or more options per cell, then you need to mark each option. The game provides this opportunity. In the lower right corner there are button numbers that allow you marking an empty cell with numbers.
For the cells having variants, we cannot determine the solution. Choose any cell with 2 options. Using the method of exceptions, choose one of the options as correct and continue solving the puzzle. If we chose the wrong option, Sudoku will not be solved. In this case, you’ll need to come back to the step of selecting back and choose another option. This method is very hard, since we can almost solve Sudoku and go to a dead end, and then have to go back to another option.
In case you have chosen the option for the cell, then you need to use the first method of intersections, perhaps there are cells that can be determined definitely.
Daily levels and difficulty levels
The game is divided into the following types:
- difficulty levels;
- daily levels.
At the top of the screen you can generate a difficulty level.
- Easy;
- Medium;
- Hard;
Levels are based on the number of hints. The more complex the level is, the fewer hints are given initially.
Every day we create an exclusive level and add it to the level calendar. For the passage of these levels points are awarded. You can find the players' rating on the website or in the game itself. To compete with other players, you need to sign up on the website using Facebook. Do not forget to invite friends. Good luck in solving Sudoku!
