IndeX
- Killer cages
- Indexing
The brief
Standard sudoku rules apply: each row, column, and 3x3 box must contain all the digits from 1 to 9.
Digits in cages must sum to the number in the top left corner.
Red cells are index cells: a digit in a red cell gives the location of its row number in its column, and its column number in its row. E.g. if R1C9 is 4, then R1C4 is 9, and R4C9 is 1.