Title: Modular Lightning
In the first of three puzzles of this type, modular arithmetic plays an important rule. Here, all the sums are given mod 9.
The official rules:
- The digits 1 through 9 appear in each row and each column exactly once.
- Digits in each shaded region must add to the indicated sum (mod 9).
- Squares with multiple colors contain a number that’s used in the sum for adjacent regions of each of those colors.
- Remember: numbers can repeat within a shaded region if that doesn't violate the first rule.