El Trece
- Killer cages
- Diagonals
The brief
- Normal sudoku rules apply, i.e. each row, column and 3x3 region has to contain the digits from 1 to 9 once each.
- Diagonals: On the main diagonals, digits do not repeat.
- Killer cages: Digits in a cage do not repeat and must sum to 13.