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Sudoku is a number puzzle where the objective is to fill every row, column and box (3x3 grid) with the numbers from 1-9. Each unit (row, column or box) must have each number exactly once. The game starts with a number of fields pre-filled. Your objective is to fill the rest of the fields without breaking the constraints that each number can only be once in each row, column and box.
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Settings
This implementation of Sudoku offers three difficulty settings, offering 35, 28, or 23 clues depending on the chosen difficulty. Note that the listed clues for each difficulty is only approximate, and while our Puzzle generator does its best to find the right number of clues sometimes it can't do it quickly enough, and will respond with whatever clues it did find that is the closest to the target value.
Additionally you can select if the clues are to be symmetric or not: meaning that the initial clues on the table will be rotationally symmetric, rotating 180° around the center. For easy and medium our generator will almost always find a symmetric configuration, but it's more likely that it will fail in finding a hard configuration that is both symmetric and satisfies the conditions of the puzzle. Symmetric puzzles may be easier to solve than asymmetric puzzles, which is why we provide you with the option to turn the symmetry off.
Sudoku Strategy
The basic gameplay, which will be enough to solve many easy Sudoku puzzles, is simply to look at an empty field and eliminate all numbers that are already present in the row, column and box it belongs to. In many cases this will be enough to find the correct number. And of course as soon as you've found the right number for one field, it will be easier to figure out other fields in the same row, column or box.
When you get into more difficult situations there are a number of different strategies you can use. The excellent page Sudoku Dragon has a good strategy page that covers many basic strategies as well as some advanced ones.
Controls
You click on the squares you want to put numbers in, and then either click the numbers buttons on the screen, or the number keys on your keyboard to fill them in. If the "Multinumber" button is pressed then you can put more than one number in each square, it will show as small numbers if there are more than one number in the square. However, in some cases you might want to put just one number in the square and still have it be small, if you think it should be there but are not sure. In that case, hold down the shift key on your keyboard and press the number key, if you do that there will always be a small number in the square, even if there's just one number there.
Sudoku is the 14th game created for Cardgames.io, and only the second one that is not a card game or solitaire (the other being Yahtzee). The idea of creating a Sudoku game had been around for a long time, inspired in part by Peter Norvig’s excellent article on building a Sudoku Solver. The code used to generate and solve the puzzles in this game is based on his approach. Every puzzle in the game has a unique solution and is designed to be solvable using logic, you should never have to blindly guess. The solver/generator code is available on Github, you are free to use it for whatever you want.
Need to contact us?
Any comments, complaints, bug reports, questions, or anything else should be sent to support@cardgames.io.
We can't respond to everyone, but we try to respond to as many as we can. If you just have a quick question make sure it isn't
covered in our FAQ.
You can also often get help from other users on our
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where many of our users congregate. Pop in and say hello!
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