Normal sudoku rules apply. Wherever a 2x2 area consists of two odd and two even digits in a checkerboard pattern, a little checkerboard symbol appears in its centre. If the symbol does not appear, the surrounding 2x2 does not have such a checkerboard pattern. Digits in cells that are an equal number of steps from the midpoint of a lavender line must sum to the digit on the midpoint (marked by a dot).