SUDOKU 156

I noticed in the 9x9 table :

• Every number 1, 4, 7 have 4 small box.
• Every number 2, 6, 9 have 3 small box.
• Every number 3, 5, 8 have 2 small box.

• Numbers 1, 4, 7 is easy to add in the 9x9 table.
• Numbers 2, 6, 9 is hard.
• Numbers 3, 5, 8 is very hard.

Therefore, this puzzle have hard level.