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 digits X (you have to determine which digit is X) is a chess Queen. Two Queens cannot be placed along the same row, column or diagonal of any length.
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.