Divide the grid into regions, each consisting of 9 orthogonally connected cells, such that every cell is part of exactly one region. Place the digits 1-9 exactly once in each row, column and region. Adjacent digits along a line must either be consecutive and belong to a different region or have a 1:2 ratio and belong to the same region. (A 1:2 ratio means one digit will be double the other.) If 1 and 2 are adjacent along a line, they can satisfy either condition.