Draw one or more lines from each numbered cell so that each number indicates the total length of lines that are drawn from that cell, excluding the cell itself. Lines are either horizontal or vertical and connect the centers of adjacent cells without crossing or overlapping each other, the given numbers and cells with a cross.
Grid control: To draw a line press the mouse button at a start cell and move mouse to another cell holding the button. You can additionally mark come cells with circles which are not considered when checking the solution. More details about grid control are at the help page.