Normal sudoku rules apply. Divide the grid into “galaxies”, which are orthogonally connected groups of cells that have 180 degree rotational symmetry about their centres, and do not overlap with other galaxies. All cells must be part of a galaxy. The centre of every galaxy is marked by a red dot. Digits may not repeat within a galaxy. No two adjacent cells in the grid (ie no domino) may have digits that are in a 1:2 ratio.