Fundamentals

Title: Fundamentals

Rating: 4/5

This is another toral board puzzle, to join the ranks of Prorus and Circuitry.  As a reminder about the alteration, check out the last rule below.

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.   
• 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.
• The board is a “toral board,” that is, cells at the end of one row are considered adjacent to those at the beginning of the same row; cells at the end of one column are considered adjacent to those at the beginning of the same column, and all corner cells are considered adjacent.