Normal sudoku rules apply. Placing a correct digit will clear the fog from the neighbouring cells. Guessing is not required. Lines travel orthogonally or diagonally through the centres of cells. They do not branch and do not cross themselves or each other. All given lines are a different colour. A grey dot may hide part of a line. Lines are “region-subset lines” ie The 3x3 box borders divide lines into segments. If a digit appears in a segment of length N, it must appear in all segments of length N or greater on that line. All lines have at least two segments. In addition, a digit on a line indicates the number of times that digit appears on that line.