Or is it?
- Indexing 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.
- Index Lines: Each turquoise line is an Index Line, i.e. the digit in the Nth cell along such a line (starting from the diamond) indicates the position along the line where the digit N appears. For example, if a diamond cell contains a 3, the third cell along that line must have a 1.
- Up to N-sums: A clue outside the Row or 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.)