Click mouse to change the position of the spot Click 1 to draw a line; Click 2 to draw a line and one more at the back; Click 3 to draw a line and a right angle with the anti-clockwise side; Click 4 to draw a line and a right angle with the clockwise side; Hold 5 to draw a triangle. The spot, the place of your mouse when your click 4 and the place of your mouse when your release 4 will be the position of the angle; Click q to undo the lines;
