New puzzle DIAGONAL Sudoku X 16x16 #2 Very Difficult to play online for free
These sudoku variants are only offered in 4x4 (16 squares) as the examples below show. This is a variant where the diagonals must also contain the numbers 1-16 in addition to all vertical and horizontal rows, as well as each 4x4 box, must contain the numbers 1-16 once. This sudoku variant is no worse to solve than a standard sudoku puzzle.