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Difficulty
Easy
Medium Hard Evil Impossible
Check for solution:

00:05


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Well Done
Time used:
01:00s
Hints used:
1
Mistakes detected:
2
Total time:
01:30s
Puzzle statistics: Average time:
01:50s
Best time:
00:56s
You're in the top:
3%

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Hint



Sudoku Genius
Classic Numbers Puzzle
by Appgeneration Software





PLAY SUDOKU ONLINE

Get set, relax and prepare to challenge your brain with this number-placement
puzzle anywhere and anytime. Start by choosing any of the four different levels
of difficulty:

 * Easy
 * Medium
 * Hard
 * Evil
 * Impossible

The harder the level, the fewer allocated numbers at the beginning of the
puzzle.

Beginners can start by choosing the easy level to get acquainted with the
digits, the grid and the rules of the puzzle. If you feel confident in your
skills from the beginning, you can put them to test with the medium level and
face demanding challenges right from the start. Experts and pros can also have
their fun and enjoy playing with the numbers and possibilities with the hard and
evil levels.

Time is not a constraint and only logic is necessary. Don’t rush, analyzed all
your possibilities and slowly work your way to fill the grid. Let the cogs on
your brain spin and enjoy this relaxing yet challenging puzzle.


WHAT IS SUDOKU

Sudoku is a number-placement puzzle widely popular in the world, credited with
helping to keep the brain active and healthy.

The basis of the game originated in Switzerland in the 18th century when the
mathematician Leonhard Euler developed the concept of Latin Squares used in
statistical analysis. The modern Sudoku as we know it nowadays, however, using
digits instead of the Latin alphabet, was most likely the creation of Howard
Garns, an architect from Indiana who first published his version of the game in
the Dell Magazines in 1979.

Its widespread popularity didn’t come until the game reached Japan in 1984 when
Nikoli published it under the name “Suuji wa dokushin ni kaguru” (The numbers
must remain single) in the Monthly Nikolist Magazine. Nikoli also introduced two
new rules that became essential to the game as we know it today. The first was
the concept of symmetry. The given numbers in the beginning must create a
pattern in their allocated squares to make the game more visually appealing to
the players. The second and most import rule is that no more than 32 numbers out
of the 81 can be given away, as the goal becomes too easy to reach above this
threshold. As the game’s popularity increased in Japan, its designation was
eventually shortened to include only the characters for number (数 - Su) and
single (独 - Doku), resulting in the name by which we now know it, Sudoku.

Nikoli’s sudoku version later spread throughout the world thanks to Wayne Gould,
a retired Hong Kong judge who first encounter the game in a Tokyo bookstore and
later published a book with his own puzzles in the UK and the US. Later,
newspapers all over the world started including these games in their
publications.


HOW TO PLAY SUDOKU

Sudoku is played on 9 x 9 grid, divided into 3 x 3 squares separated from each
other by thicker lines. The goal of the game is to fill each cell with a number
from 1 to 9 making sure there are no repeated digits in any column or row in the
grid nor within the square itself.

The game starts with the grid partially filled and the player must find the
remaining numbers based on the position of those already given. The difficulty
of the puzzle varies according to the number of filled cells at the beginning of
each game.


SUDOKU TIPS 


NAKED SINGLES

Write down every possibility for each cell. If when you cross the rows and
columns you find a blank space with only one possibility, you have found a naked
single and the right answer for that cell. 


HIDDEN SINGLES

Hidden singles are in fact naked singles that occur once you add a new digit to
a row or a column. Keep your pencil notes updated and check them often through
the game to find these. 


NAKED PAIRS

These occur when you have two identical pairs of candidates in a single row or
column. Even if you do not know their right placement, you can identify without
a doubt their position in the grid. Thus, you can eliminate those digits from
any other possibilities in that row or column. 


HIDDEN PAIRS

Hidden pairs are cells with two identical candidates positioned in opposite
corners of one square and nowhere else in the region. This means that you can be
certain that those two blank spaces can only be filled with one or the other.

They are called hidden pairs because there might be other candidates for the
same cells which can make them hard to spot. 


NAKED TRIPLES

Naked triples occur in rows or columns when you have three candidates that
overlap. The digits do not need to be the same for every cell, but this will
tell you that those will be for certain in that row or column, allowing you to
eliminate other possibilities.

For example, if you have the combination of 6/8 – 8/4 – 6/4 in the same row, you
know that these 3 digits will be in that row regardless of their right
placement. You can then eliminate these numbers from your pencil notes on the
remaining rows of their square.


UNLOCKING POSSIBILITIES

The grid in Sudoku is always changing. Every time you place a digit, a number of
possibilities open on other blank spaces. Check the ones immediately affected by
the filled cell and you might find their answer right away. Pay attention to the
neighboring squares also, as their structure is very likely to have changed too.


DON’T TRY TO GUESS

Sudoku is a simple game of logic. Guessing should be your very last resort as it
can easily throw off the puzzle and make it unsolvable.


KEEP YOUR GRID CLEAN

Review and update your pencil notes often to avoid cluttering the grid with
possibilities. The more candidates you note down, the noisier the puzzle will
become which not only will it make it more stressful, but it can prevent you
from finding easy numbers like naked singles.


PRACTICE MAKES PERFECT

Your skills will improve after each Sudoku challenge. With time, the brain
becomes faster and better at finding the weakest spots, possible candidates and
crossing all the information of rows and columns at once to find the solution.
Its increased performance also extends to memory and pencil notes become less
important.

A beginner challenge that once looked anything but easy can turn ridiculously
quick to solve after just a few puzzles.

Sudoku is such a simple and yet popular game precisely because it is a battle
against oneself and you can experience the results of your training firsthand.


SUDOKU PUZZLE SOLVING STRATEGIES


CROSSHATCHING

Focus on each square at a time. Compare the missing numbers with those on the
rows and columns of the grid that reach the square. If they contain any of the
missing numbers, you can eliminate the blank cells on the square from that row
or column. 


COUNTING

Count the numbers of each row to find the missing ones. Repeat the process at
each column. Cross the likelihood of each number’s position with the contents of
the square to increase probabilities or to find the right answer.


THE CERTAINTY OF THE UNCERTAIN

Even when the placement of a number is not certain, you can sometimes determine
that it will be without a doubt positioned in a certain row or column. Take note
of that position and use it to eliminate other possibilities in the squares
connected to that column or row in the grid.


THE X-WING METHOD

This strategy is normally used in the hardest levels of Sudoku. The goal is to
eliminate possibilities (pencil notes). You can use it when you have the same
candidate in 4 spots that form a square or a rectangle when connected by row and
column. If you connect each of the extremities of the square you discover that
one of those pairs will be the correct one in the end. If you test either of the
possibilities, you might be able to eliminate the digit being analyzed from
other pencil notes in different cells.


THE SWORDFISH METHOD

To apply this method, you must have 2 identical candidates in the same row, in
three different rows. These candidates must also be connected by column,
regardless of the shape they create.

When you connect the different possibilities, you should have a closed chain. In
the end, you will have only two sets of possible answers. You can then test
these sets and eliminate the digit you are working with from any cell that
becomes impossible under the two possibilities.


THE JELLYFISH METHOD

The Jellyfish is an upgraded combination of the Swordfish and the X-Wing
methods. In this case, you must have the same candidate in four columns in only
four different rows. Connect the cells to discover the sets of units that could
come out of the different possibilities. The candidates that become impossible
when any of the sets are tested can be eliminated.


CHECK OUR LATEST ARTICLES


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challenging, …

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SUDOKU UNIQUE RECTANGLE: TYPES AND PATTERNS

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