Residual X-Rays
by FullDeck and Missing a Few Cards
Heartburn
- Modular lines
- X-sums
The brief
Normal sudoku rules apply. Modular lines: Modular lines: every set of three sequential digits along a line must contain a complete set of residues modulo 3, i.e. one digit from {1,4,7}, one from {2,5,8}, and one from {3,6,9}. Digits on two-cell lines cannot be from the same residue set. Digits may repeat on a line if allowed by other rules. X-Sums: Digits outside the grid give the total of the first X digits in the row or column (starting next to the number outside the grid) where X is the first digit along that row or column. Every X-sum forms a hidden modular line of length X.