HINTS:

YOUR   ENGINE  CAN  PATROL  TO ANY POINT YOU
CHOOSE. SELECT AN ENGINE BY CLICKING IT WITH
THE  LEFT  MOUSE BUTTON, THEN PRESS AND HOLD
THE   CONTROL  KEY  ON  YOUR  KEYBOARD  (THE
POINTER WILL CHANGE ITS SHAPE) AND CLICK THE
POINT YOU WISH TO PATROL TO. THE ENGINE WILL
BE MOVING TO THIS POINT AND BACK AGAIN.
