Criss Cross
- Kropki dots
- Modular lines
The brief
Standard sudoku constraints: every row, column, and box must contain a complete set of the digits 1-9.
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 may repeat on a line if allowed by other rules.
Kropki dots: Digits separated by a white dot are consecutive. Digits separated by a black dot are in a 2:1 ratio. Not all possible dots are given.