Normal sudoku rules apply. Draw in lines that move orthogonally from cell to cell. Two circles of the same colour are start and end of a line. Lines may not intersect themselves or other lines. The lines drawn in the grid act both as a Region Sum Line (RSL) and a Modular Line (ML). Additionally, digits CANNOT repeat on a line. Region Sum Line: Along a RSL line, box borders divide the line into segments with the same sum. Every set of three sequential digits along a ML must contain a complete set of residues modulo 3, i.e. one digit from {1,4,7}, one from {2,5,8}, and one from {3,6,9}.