Ruff and Reddy in the Space Adventure

During play, hold down 'HELP' and press the left mouse button.  
A secret screen will appear.  While still on the secret screen press
the 'LEFT AMIGA' key 5 times and then press 'SPACE' to go back to
the game.  If you hold 'HELP' and press the left mouse button again,
you will notice that the secret screen now shows that the cheat mode
is now on.  You will now be invincible.