Normal sudoku rules apply. Adjacent digits on a green line differ by 5 or more. Divide the grid into non-overlapping rectangular regions so that each region contains exactly one small clue (found in the top left corner of some cells). Four regions cannot share the same cell corner. Digits may not repeat within a region and sum to that region's small clue. The digit placed in a small clue cell gives information about that region: 1–4: The region has a greater width than height. 5: The region is a square. 6–9: The region has a greater height than width.