Normal sudoku rules apply. The 3x3 box borders divide a blue line into segments. The sum of the digits along each segment is the same for that line. Different lines may have different segment sums. Eg r4c7+r4c8 = r1c6+r2c6+r3c6 = r1c7+r2c8+r3c9+r3c8
Normal sudoku rules apply. The 3x3 box borders divide a blue line into segments. The sum of the digits along each segment is the same for that line. Different lines may have different segment sums. Eg r4c7+r4c8 = r1c6+r2c6+r3c6 = r1c7+r2c8+r3c9+r3c8