Normal sudoku rules apply. Draw two closed loops in the grid that don't intersect themselves or each other. A loop travels horizontally or vertically between cell centres. Each loop must be situated entirely on one side of the highlighted diagonal and is a mirror image of the other with respect to that diagonal. A digit in a grey cell gives the number of cells in its row (or column, because of the symmetry) that are NOT part of either loop. Adjacent digits along either loop must have a difference of at least 5.