This theory is explained on this page .

lvl6_1		lvl6_2		lvl6_3
lvl6_4		lvl6_5		lvl6_6		lvl6_7

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Each difficulty level.

• Exercises

• 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.

• animalsudoku(level_2,3,4,5)

  Sudoku to use the illustration in substitution for a number.