Divide the grid into regions of orthogonally connected cells. Each cell should contain a number equal to the size of its region (i.e. the number of cells in its region). Each number from 1 to 9 must be present in the grid. Cells adjacent to each other can't be consecutive (not even diagonally). Cells separated by a black dot must contain digits with a 1:2 ratio (ie one digit must be double the other).