On the title screen, type "YOU CALLING MY PINT A POOF?" and press
'RETURN'.  The screen should flip upside down to let you know it
worked.  The ? can either be typed '/' or hold shift and press '/'.
Start the game and you will notice that the disk access stops but
the game doesn't start.  Press 'F1' and level 1 will load.  This
will give you invincibility and access to the following keys during
play:

         'DEL'_______to kill enemies currently on the screen.
         'F1'_________________________________to skip levels.

NOTE:  Works fine on a 500, but I had to type it a few times on my
       1200 to invoke the cheat.

The following did not work with the version I have:

Typing any of the following on the title screen:

         "LEVEL ONE PLEASE"__________________Go to level one.
         "LEVEL TWO PLEASE"__________________Go to level two.
         "LEVEL THREE PLEASE"______________Go to level three.
         "LEVEL FOUR PLEASE"________________Go to level four.
         "LAST LEVEL PLEASE"________________Go to last level.
         "GIVE ME MORE HEALTH PLEASE"_________Lots of energy.
         "I DO NOT WANT TO DIE PLEASE"__________Invicibility.

On the high score table, type "NEIL HARDING" as your name for
something funny.

Play two player game and get both players killed until you have one
credit left and the "continue" message is displayed on both sides
of the screen.  Press both fire buttons simultaneously and you will
get infinite lives.