SUDOKIS - Makes Sudoku understandable

Do you like Sudoku? Then you're sure to love SUDOKIS.

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SUDOKIS - Create your own Sudokus - Determine difficulty levels - Chosse one of 100,000 SUdokus - Solve Puzzles step by step-by-step - Get help at every step - Learn a lot - And have much funn
One simple GUI - Many possibilities
You have got the creativity - SUDOKIS has the user guidance and computing power

SUDOKIS has a simple GUI, everything is included here.

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The SUDOKIS application has many Sections
Rating: know your Sudoku
Editor: Create your own Sudoku
Multiple purposes: Detailed information for many functions
Buttons only: No complicated pull down menus
Rating rest game: The optional cheating mode
Game field: Your solution step by step
Fingerprint: Fastest way of editing
Log field: Step by step solution can be replayed

Videos

Create an individual, valid Sudoku with a given level of difficulty in less than a minute

50 levels of difficulty

SUDOKIS divides Sudokus into 50 different levels of difficulty. 5 main difficulty levels, each with 10 sub-difficulty levels.

  • Easy 1-10
  • Medium 1-10
  • Difficult 1-10
  • Very Difficult 1-10
  • Extremely Difficult 1-10

In addition, there are two levels outside the range, Extremely Difficult 11 and Extremely Difficult 12, where there are hardly any analytical possibilities to find solutions.

The level Easy and Medium are level for children, or for solving Sudoku puzzles in a relaxed way. Easy Sudokus can be solved with only one rule, Medium level with two rules.

Take your time to solve the Difficult and Very Difficult levels.

Extremly Difficult level are typically only suitable for people who like pain.

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Do you have a child in kindergarten or elementary school who already knows the numbers from 1-9? That's the perfect age to start with Sudoku. Start with easy 1. Every field can be solved directly. Your child will be proud to be able to solve Sudoku puzzles.

Wondering why similar-looking Sudoku puzzles can be so differently difficult? That's true, just try it out!

SUDOKIS also categorizes invalid sudokus. These Sudokus should not be played, but you should understand them in order to create your own Sudokus.

  • Incorrect: There is a direct rule validation within the numbers
  • Unsolvable: The Sudoku looks valid at first glance, but there is no solution
  • Not unique: This sudoku is not valid, because it has more than one solution
  • Solved: There is obviously nothing to do
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Please refer to chapter 50 levels in detail for more detailed explanations of the difficulty levels.

Create your own Sudoku

Creating your own Sudoku is a very creative task. And with SUDOKIS, creating Sudokus is made easy. Just move the cursor to the fields to enter numbers.

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Enter the numbers of your Sudoku in the Editor
Always check the actual rating
If you do not care about the number to be entered as long as it is valid, use the double-click. This makes sence for the first numbers you enter. Later you sould check the effects of your input on the number of the solutions in advance
Move the cursor to the next position to be edited
For each possible number, check what happens to the rating before you enter the number in the field.
Entering the number 9 is a good choice, it reduces the number of solutions from 642435 to 26091
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Enter the number 8 here
You will receive a valid Sudoku with one solution
Complete the last two fields to get a nice smiley face
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Wonderful! We just created our first Sudoku - It is very pretty!
But it is rated easy 7. This is too easy! This is no fun! And now?

Up to this point, the way to create a Sudoku is quite simple. Move the cursor to any field, see what effect changing this field has and decide whether you want to change it or investigate other fields. Now we seem to be stuck. The only way forward now seems to be to withdraw entries and try again. Trial and error.

Okay, we can't get by completely without trial and error. But can't SUDOKIS support me in this? Are there any hints as to where I should move the cursor next?

Yes! SUDOKIS gives hints, and can even help with trial and error.

Each field gets its own color. The colors are calculated in two passes, a first fast pass and a second exact pass.

Colors after first pass

Colors after second pass

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The green color indicates that you can make a change to this field and after this change the Sudoku is uniquely solvable.
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The turquoise field can appear on uniquely solvable Sudoku puzzles. It indicates that it is possible to create a new uniquely solvable Sudoku with a higher level of difficulty by changing the number of this field to a different number.
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The strong green field can appear on uniquely solvable Sudoku puzzles. It indicates that it is possible to create a new uniquely solvable Sudoku with a higher level of difficulty by deleting the content of this field or by setting a number on an empty field.
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The pale green color indicates that you can make a change to this field and after this change the Sudoku is uniquely solvable. However, you cannot increase the difficulty of the Sudoku by making a change.
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The yellow color indicates that you cannot make any changes to this field so that the Sudoku is then uniquely solvable, but it is possible to create another Sudoku with several solutions.
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The strong yellow color indicates that you cannot make any changes to this field so that the Sudoku is then uniquely solvable, but it is possible to create another Sudoku with fewer solutions.
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The pale yellow color indicates that you cannot make any changes to this field so that the Sudoku is then uniquely solvable, but it is possible to create another Sudoku with several solutions. However, it is not possible to reduce the number of possible solutions by making changes to this field. But beware: the calculation limit here is 1000 solutions.
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A red color can only occur with invalid Sudokus. The red color indicates that it is not possible to make the Sudoku valid by making a change in this field.
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The pale red color means that it is not possible to get a valid Sudoku with a change to this field, but it is possible to get a Sudoku which is unsolvable even though it has no direct rule violations.
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The strong red color means that the Sudoku has direct rule violations and it is not possible to correct all of them by only changing this field.

Let's continue with making our Sudoku more difficult. At this point, we first look around for turquoise fields. The rating can be increased by changing these fields to different numbers without deleting the content of the field completely.

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Entering a 4 at the position of the cursor makes the Sudoku easy 8
If you enter an 8 here, the Sudoku will be medium 8
Is it possible to create an even more difficult Sudoku?
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If you enter a 2 here, the Sudoku will be difficult 1
The difficulty can only be further increased by deleting fields. But this destroys the beautiful smiley face.
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We need new ideas. We now temporarily destroy the validity of the Sudoku by entering a 4 here.
This will make the SUdoku unsolvable
Entering a 8in this field will solve our temporary problem.
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Now we got a beautiful very difficult 4 Smiley Sudoku

Admittedly, it may take a few attempts to find the right path to the optimum solution. But unlike other fully automatic Sudoku generators, SUDOKIS allows you to put your creative ideas into practice. You won't lose track of logical dependencies. And with a little practice, you will learn to read the SUDOKIS hints quickly.

Would you also like SUDOKIS to generate Sudokus for you fully automatically? But not just any Sudoku? You have told SUDOKIS which pattern your Sudoku should have. Would you like SUDOKIS to automatically calculate whether there are any other Sudokus with this pattern? You don't have to do anything else, just leave the focus on the editor and see what SUDOKIS finds after the second pass of the color calculation is finished.

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In this image it is shown, how SUDOKIS searches for Sudokus with a given pattern.
Keep the focus on the editor
If your pattern has enough set values, you will get many results after a few seconds.
If you are looking for a Sudoku for this pattern with a certain level of difficulty, you may haveto wait consiterably longer for a result.
Select Sudokus of the desired rating, and look at the result
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You get many results after only one second
For some rating level you need to wait for a long time.

To calculate the results, SUDOKIS uses a non-intelligent approach of filling the fields with random values. Pure computing power usually produces results. However, whether results are delivered depends to a large extent on whether a sufficient number of values can be filled.

Obviously, it is not possible for any algorithm to try out all possibilities. Sudoku has 1081 possibilities to fill the fields. This corresponds approximately to the number of atoms in the entire universe. Even if you restrict the pattern to 21 fields, 1021 values still have to be tried. This corresponds approximately to the number of atoms in the entire earth.

Nevertheless, the algorithm delivers results quickly in many cases. If the number of fields is greatly reduced, you often simply have to wait longer for calculation results. If too few fields are specified, the algorithm cannot recognize this, it simply does not find any results even after hours. The algorithm does not start at all with fewer than 17 pre-assigned fields. It is known that there are no Sudokus with fewer than 17 fields.

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For the smiley Sudoku, it is noticeable that even after several hours we have not found any Sudokus in the difficulty levels Easy 1 - Easy 6. The question is whether these Sudokus exist or whether it is just a needle in a haystack that is difficult to find.

Easy 1 means that every field can be solved directly. To be able to solve a field directly, you need 8 other fields in the area of influence with 8 different values. However, if there are fields with fewer than 8 fields in the area of influence in a pattern, then there cannot be a Sudoku in which this field can be solved directly. In the case of the smiley, there are 24 fields that have fewer than 8 fields in the area of influence (these are marked in red). This means that the difficulty levels Easy 1 to Easy 4 can never be found. For the difficulty levels Easy 5 and Easy 6, we do not know whether they exist.

Below you can see the effect on the calculations if SUDOKIS has fewer fields available than with the smiley.

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This Image shows a Sudoku with e heart pattern.
Finding Sudokus in the smiley pattern is quick, it takes a little longer for the heart pattern. After 1 Minute you can get 29 results in this example.
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And it takes even longer if you delete the bottom of the heart.

The SUDOKIS algorithm is optimised to find solvable Sudokus. It is not easy to find extremely difficult Sudokus outside the rating scale. If you want to create such extremely difficult Sudokus with SUDOKIS that nobody can solve them, you should specify a pattern that makes such Sudokus possible. Sudokus that contain many diagonal lines have the potential to be that difficult. Just try it out.

While you create Sudokus in the editor, SUDOKIS uses computing power in the background to support you. This also means that the process of creating Sudokus requires a lot of energy. On notebooks it is better not to use the battery mode. This note only applies to the process of creating new Sudokus. There are no long-lasting computationally intensive tasks running if you have a few Sudokus analyzed or solve them yourself.

Now you can use your creativity to create beautiful Sudokus with a well-defined level of difficulty. Here are some suggestions.

Image Clover
Image Heart
Image House
Image Fish
Image Man
Image Fir tree
Image Chandelier
Image Boat
Image Cross
Image Snowflake
Image Rose
Image Star
Image Sandglass
Image Umbrella
Image Apple
Image Diamond

Have fun solving your own Sudokus.

Load or save Sudoku

Do you want to save the newly created Sudoku? So that you can play, print or share it later? No problem!

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You can not only load your own Sudokus, SUDOKIS offers a variety of Sudokus on the WWW. You will find 100,000 Sudokus sorted by difficulty in the embedded web browser. 2,000 for each difficulty level. Simply click on the Sudoku to start it. Please also check the custom section. Here you will find beautiful Sudokus.

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Solve Sudoku by yourself

Being able to solve Sudokus yourself is a key feature of SUDOKIS. Take a look at the step-by-step instructions on how to solve it. These instructions initially refer to solving without significant help from SUDOKIS. You can find out how to get more in-depth help in the chapter Get help with solving Sudokus

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In some difficult situations, it is necessary to draw on the Sudoku field to find the right next step. For future versions of SUDOKIS it is planned to offer the possibility to draw. If you already need this feature now, you can do it the classic way with paper and pencil. To do this, print out the current Sudoku board with the settings shown here in the print dialog and you will receive a printout of the current situation.

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Get help with solving Sudokus

You've done a good job solving the Sudoku so far, but now you're stuck.

If you ask SUDOKIS for help, it will tell you the next possible rules. SUDOKIS doesn't care if you have made a mistake and the Sudoku is no longer solvable. You should therefore check the solvability first.

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Print Sudoku / Make PDF

To be added.