The room of sudoku hard.

1. This web site is for people who already know the rules of SUDOKU puzzles. And for those who are looking for more fun, higher quality SUDOKU puzzles.

   SUDOKU puzzles are pretty popular right now worldwide. There are so many SUDOKU puzzles sites in the world. But, there are only a few sites that have high quality SUDOKU puzzles. There's only one reason. This is because SUDOKU puzzles can be easily created by anyone with a little program knowledge. But it is not easy to develop software that creates truly interesting SUDOKU puzzles. So today, we have too much SUDOKU puzzles sites ; we need to select rare good sites from too much bad ones.

   The SUDOKU puzzles in this site are high quality and handmade tastes. The reason is the algorithm developed for this site. I purposely use not the mechanical algorithm but the algorithm that the same way how humans create SUDOKU puzzles. Therefore, This site's puzzles has handmade tastes.

   And there is another reason why the SUDOKU puzzles on this site are fun. No matter how difficult it is, we can solve the sudoku puzzle on this site without using assumption logic. There is the opinion that very hard SUDOKU puzzles need assumption logic. In my opinion, it is wrong. The SUDOKU puzzles that need assumption logic are only incomplete puzzles. The assumption logic is a solution that relies on chance without reasoning or rationale. There are no SUDOKU puzzles that requires assumption logic on this site. All puzzules on this site can be solved by logical conclusion.

   Development of handmade algorithm for this site and expelling of assumption logic. These two things make the sudoku puzzle of this site very very fun.

In Japan, which is already a developed country in SUDOKU,the Japanese version of this site has a strong popularity among sudoku lovers. Please enjoy the high quality sudoku puzzles on this site.

For Medium class(level2~5) sudoku is the Today's seven.Hard class is the Today's hard.Easy class is the Today's level1.

3. Please write your name when you win. And click New button!

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   I update latest Sudoku at each difficulty level irregularly.

   by S Ishikawa

Each difficulty level.

• level6(2020/6/18 up)

  For expert

• level7(2020/6/18 up)

  For expert

• level8(2020/6/17 up)

  For great expert

• level9(2020/9/25 up)

  　　　

  For great expert

• Zero(2020/6/22 up)

  For great expert.The Sudoku that one number cannot write.

• How to solve Sudoku

• animalsudoku(level_2,3,4,5)

  Sudoku to use the illustration in substitution for a number.