Normal sudoku rules apply. Blue lines are Region Sum lines. In each box visited by such a line, the digits must sum to the same total, to be determined. The target sum will potentially be different for each line. XY Difference Pairs rules apply. If two cells are separated by a diamond, the digits must exhibit a difference equal to the leftmost or topmost digit sharing a row or column with them. For example, the difference between R9C34 = R9C1, and the difference between R23C1 = R1C1. Not all possible diamonds are necessarily given.