HINTS:

SELECT YOUR  ENGINE BY CLICKING IT WITH  THE
LEFT MOUSE  BUTTON.   THEN HOVER THE POINTER
OVER  THE CANNON  TO  CHANGE  THE  POINTER’S
SHAPE AND  CLICK IT  WITH  THE  RIGHT  MOUSE
BUTTON. THE ENGINE WILL MOVE ON AND HITCH UP
THE CANNON.  NOW HOVER THE  POINTER OVER THE
BOULDER  IN  THE  PATH.   AFTER  THE POINTER
CHANGES  ITS SHAPE,  CLICK  THE  RIGHT MOUSE
BUTTON AGAIN.  THE ENGINE WILL  MOVE  TO THE
BOULDER AND DESTROY IT.
