Normal sudoku rules apply. The grid is covered in fog. Placing a correct digit will clear the fog from the surrounding cells. Values of the pair of cells with an equal distance to the circled centre of a lavender line sum to the value in that central cell. Shade some cells orange such that all shaded cells are orthogonally connected and all unshaded cells are orthogonally connected. No 2x2 area may be fully shaded or fully unshaded. The value of a shaded cell is its digit. The value of an unshaded cell is zero minus its digit (a negative number).