Battenburgs and Mod-Zip-Birds
- Zipper lines
- Modular 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.
- Battenburg: Whenever 2 odd and 2 even digits form a 2x2 checkerboard pattern (e.g. R1C2 and R2C3 even, R1C3 and R2C2 odd), a Battenburg marking is given. If there is no such marking, the above pattern is not allowed.
- Modular Zippers: All teal lines are both Modular and Zipper Lines. Every set of three adjacent digits along the line has to contain one digit of (1, 4, 7), one of (2, 5, 8) and one of (3, 6, 9). Moreover, digits at an equal distance to the center, which is marked with a dot, must sum to the digit at the center.