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About sudoku

Sudoku is a logical number game which is increasingly gaining in popularity. It requires no previous knowledge and is easy to understand.

The classic 9-by-9 sudoku grid must be completed in such a way that

in every row
in every column
in every 3x3 block

every number from 1 to 9 appears exactly once.

There is a definite solution for every suggested sudoku grid using the pre-given numbers.

Sudoku instructions

You can fill in the Sudoku grid easily using a mouse or a touchscreen to select candidates or enter a solution into an empty field.

First you need to activate an empty field by clicking or touching.

The background color changes to show that the field is active and candidates from one to nine are shown as possible solutions.

Depending on how you play, you can use the option ‘Reverse candidates’ to toggle activation of the candidates.

On the left hand side of the puzzle you can use the numbered buttons to control the candidates.

As long as the field remains active, you can use these buttons to activate and deactivate the candidates. Alternatively you can activate and deactivate candidates by clicking on them directly using the mouse.

On the right side of the puzzle you can use the numbered buttons to confirm a number as the solution. Alternatively you can double click on a candidate to confirm it as a solution.

You can easily change a solution field back to a candidate field by clicking or touching it.

By clicking the ‘Check puzzle’ button all of the confirmed solutions are checked. Numbers which do not match the solution are indicated and must be corrected.

You can use the ‘Check puzzle’ button as often as you like.

Scoring system

To make playing more fun and competitive, our scoring system is based on the number of puzzles you solve and the difficulty level.

The maximum number of points per day is limited to 5. Puzzles are only counted which were started and solved on the same day.

Points matrix

You can see how many points you can earn by solving sudoku puzzles for each difficulty level in our points matrix. As soon as you have reached a certain number of points, you qualify for the next level. The system is designed so that you can move to the next level quickly by solving sudoku puzzles regularly.

Difficulty level	points
Very easy	0
easy	0.5
medium	1
difficult	1.5
Very difficult	2

Levels table

To reach the first level you will need two points. For each subsequent level, the number of points required to reach the next level increases by another two points.

Level	Points required for next level	Total points
0	2	0 - 1.5
1	4	2 - 5.5
2	6	6 - 11.5
3	8	12 - 19.5
4	10	20 - 29.5
5	12	30 - 41.5