New Sudoku by pattern Sudoku X (DIAGONAL SUDOKU) 16x16 #4 Very Difficult to solve online for free
Diagonal Sudoku template very similar to regular Classic Sudoku.
It involves placing the digits 1-16 so that all vertical and horizontal rows contain the digits 1-16 once, and that each 4x4 square also contains all the digits once.
In the pattern, an additional cross area is added to the 16x16 grid. Sixteen gray cells must also contain numbers from 1 to 16.