Normal sudoku rules apply. Fog covers the grid. Placing a logically deduced digit in a cell lifts fog from that cell and possibly other cells. Spiral Galaxies: Divide the 9x9 grid into “galaxies” of orthogonally connected cells; each galaxy is180° rotationally symmetric about its centre – ALL galaxy centres are marked with a square. Each cell is part of exactly one galaxy. Digits don't repeat in a galaxy and sum to the value on its central square clue. Circled digits count the number of cells in their galaxy.