Author: Andrey Bogdanov
Fill in the grid with digits from 1 to 9 putting one digit per a cell. Each row, column and outlined area should contain every digit exactly once. All places where a 2x2 square forms a Checkerboard pattern of Odd and Even digits are marked with Battenberg sign.
Grid control: Click at a cell reveals the value chooser. Click at the selected value changes the state of the cell. More details about grid control are at the help page.