Normal sudoku rules apply. It must be determined whether each white dot is a kropki dot or the centre of a galaxy. The two digits joined by a white kropki dot have a difference indicated by the number on the kropki dot. A galaxy is a group of orthogonally connected cells, that has the white dot at its centre and is rotationally symmetrical through 180 degrees. The number on the central dot of a galaxy indicates the number of cells (N) in the galaxy. This galaxy must contain all the digits from 1 to N. Galaxies also function like region sum lines; digits within each 3x3 box sum to the same amount if they are within the same galaxy. This region sum may be different for different galaxies. Galaxies cannot share cells with any other galaxies or cells joined by a kropki dot.