Normal sudoku rules apply. Digits on “region sum lines” (marked in blue) must have an equal sum N within each 3x3 box they pass through. (eg r7c3 [box7] = r6c2 + r5c2 [box 4]) Cells separated by a V must contain digits summing to 5. Not all V clues are necessarily given. Digits cannot repeat along the marked purple diagonals.