For invulnerability in this game, use the DOS utility DEBUG.
First backup your game to be edited, then type the following
from the dos prompt:
ren e:\disk3.ovl cheater.cht
debug e:\cheater.cht
e 1ca7 7b
e 96be 83 3f 00 7e 07
w
q
Then rename CHEATER.CHT back to its previous name.
