Normal sudoku rules apply. Cells separated by a white dot must contain consecutive digits. Along each blue line, each time that line passes through a 3x3 region, the sum of the digits on that pass sum to the same value. If the line passes through a 3x3 region multiple times, each pass is summed separately. Eg on the innermost line: r3c4+r3c5 = r4c5+r4c6 = r4c7+r5c7 = r5c6+r6c6 = r7c6+r7c5 = r6c5+r6c4 = r6c3+r5c3 = r5c4+c4c4.