Also known as:
Diagonal-Sudoku, Kosegenli, Sudoku Diagonal, Sudoku X, Sudoku X-tra
A standard Sudoku, except that the numbers 1 to 9 also appear on the main diagonals. The additional rule ought to make the puzzle easier for solvers, but often this is not the case. As with many of the good Sudoku variants, the additional assistance that the rule provides is cancelled out by fewer starter digits.