The asimov archive has cracked images of this shooter game by Magnum
Software.  But they will not run on a 65c02 or any emulator I've
tried.  I traced the code with a debugger and developed these patches.

There are two indirect jumps used, JMP ($02FF).  These JMP's use the
page boundary bug of the original 6502.  A bogus high order byte is
stored at $300, the real one at $200, apparently intended to mislead a
potential cracker.  Of course, this won't work on a 65c02 machine.
  T  S  B	From		To
$03 03 6E	6C FF 02	4C 7D 0B
$05 07 4B	6C FF 02 	4C 08 08


This fixes a bug which trashes the X register prior to track
re-reading.  X holds the slot# (usually $60).
Many emulators had trouble with this.
  T  S  B	From		To
$05 03 84	A6 0D 86 1B	A5 0D 85 1B
$05 03 88	A6 0E 86 1C	A5 0E 85 1C


Defeats a nibble count check (addr0 prolog to addr0 prolog).
Apparently, this wasn't a problem with a physical cracked disk.
Many emulators had trouble with this.
  T  S  B	From		To
$05 05 BB	A5 0E		18 60


Defeats some kind of disk access related check.
Emulators which use authentic disk speed had trouble with this.
  T  S  B	From		To
$0A 07 2D	A9 4F		D0 25


Fixes a bug which causes a hang or crash after winning the game.
  T  S  B	From		To
$08 03 6E	48 68 48 68 48	EA EA EA EA EA
$08 03 78	68		EA

Occasionally the game would hang in a loop during play.  I'm not sure
if this is a game problem or an emulator issue.

What started out with just a little poking around turned into a minor
project.  I got more satisfaction hacking the code than playing the
game itself.  It's interesting to see the incompatibilities that come
up when going from a physical machine to an emulated environment,
mostly disk emulation.

And finally, here's a cheat for infinite lives.
This was trivial to figure out after all the above.
  T  S  B	From		To
$0A 05 F1	4C FB 0B	EA EA EA


Chris