Author: Sashika
Draw few rectangular loops through the centers of unshaded cell so that every unshaded cell is used. The sides of different rectangles may intersect each other, but not turn at their intersections or otherwise overlap. Each given circle should be in a corner of a rectangle. If the circle is black, then the corresponding rectangle must be square. If the circle is white, then corresponding rectangle can not be square.
Grid control: To draw a line press the mouse button at a start cell and move mouse to another cell holding the button. More details about grid control are at the help page.