Normal sudoku rules apply. Digits along an arrow sum to the digit in that arrow's circle. Numbers in the corner of cages indicate the number of cells in that 3x3 Box that form "wormholes" with other boxes. A cell in a cage in Box A forms a wormhole with the central cell of Box B when the cell's position in Box A (eg top right cell) matches the position of Box B in the grid (eg top right box). Two cells in a wormhole relationship both contain the same digit. Note: Cage totals only count the number of wormholes that look out of that box and into the central cells of other boxes ie A wormhole from another box that looks into the central cell of a cage is not counted.