Normal sudoku rules apply. Colour the cells black and white such that the set of each colour is orthogonally connected and no 2x2 area is covered by only one colour. The given grey dots indicate that the two connected cells have the same colour. If a grey dot is between two black cells their digits are in a 1:2 ratio; if a grey dot is between two white cells, their digits are consecutive. ALL possible grey dots are given. [ie At the end of the puzzle, when all the cells are coloured and all the numbers are entered, two adjacent black cells may contain digits in a ratio of 1:2 only if there is a gray dot between them. Similarly, two adjacent white cells may contain consecutive numbers only if there is a grey dot between them. The following scenarios are possible without any problems: Two consecutive numbers in adjacent black cells; two digits in the ratio 1:2 in adjacent white cells; and any relationship between digits in adjacent cells with different colour.