N and N
- Diagonals
- Nabner lines
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.
- Negative Diagonal: On the negative main diagonal, digits may not repeat.
- Nabner Lines: The yellow lines are Nabner Lines, i.e. on such a line there may not be consecutive or repeated digits. For example, if a 5 lies on a Nabner line, this line may not contain another 5 and neither a 4 nor a 6.
- Ninetropy Lines: Every set of 4 adjacent digits (those might cross dots) on a hollow blue line must contain a digit from each of the pairs summing to 9, i.e. one of the subsets {1,8}, {2,7}, {3,6}, and {4,5}. A 9 may not appear on a Ninetropy line. Digits on a line may repeat if allowed by other rules.
- Up to N-sums: A clue outside the Column N indicates the sum of all digits up to the cell that contains the digit N. (The digit N itself is not included in the sum.)