Modular Lines 1
- Killer cages
- Modular lines
The brief
Standard sudoku constraints: every row, column, and box must contain a complete set of the digits 1-9.
Killer cages: Digits in a cage indicated by a dashed line cannot repeat and must sum to the total shown in the upper left corner of the cage.
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.
Example: 579219 would be a legal sequence of digits along the line provided the 9's don't see each other in the row, column, or box. This is legal since the remainders form the sequence 210210 and any string of 3 digits in the remainder contains all three possible values.