In this edition, I’m examining Planet Joker , the 1997 shooting game for Saturn. This game doesn’t have a whole lot of fans because (a) it was never released outside of Japan, and (b) it’s kind of clunky and weird.

I found some cheat codes that will make sampling this game a bit easier, however: one grants you unlimited health; another allows you to start on any stage and upgrade your weapons.

Details about the codes and how they work are below!

Unlimited health

At the mode select screen, hold Z+Left and then press Start when choosing a mode.

This will grant you unlimited health – you’ll never run out of shield capacity. For reasons I don’t understand, the shield gauge in the bottom left will go down if you take damage, but it won’t ever go to zero:

Mission select

Start a game in normal mode. At the Machine Select screen, hold Z+Up , then press A to choose your mech. Keep holding all three buttons.

If you got it right, the barebones stage select screen will appear:

StageNO allows you to pick your starting stage, of course. Values 1 through 6 are the normal mode missions. Value 7 is the time attack mission:

Value 8 is the score attack mission:

Value 9 is the boss attack mission:

The menu allows you to choose higher values, but the game will crash if you do.

ShootKind and ShootLebel (sic) affect your primary weapon. The only valid values for the former seem to be 0 and 1. The latter has a higher range, but I couldn’t quite figure out all of the distinct effects:

Technical details

I found these cheats by using my usual method:

• Locating where the game stores input by comparing memory snapshots taken (a) while holding a button, and (b) while not holding a button.
• Setting read breakpoints for the memory addresses associated with input.

For this game, the “held button” is stored at 0602b4b8 . The function at 06004390 checks it when you make a selection at the mode select screen. The logic looks like this pseudo-Python:

The 2 byte value at 0602b318 determines whether the game continually resets your health to a value of 12 during gameplay.

The function at 06006690 does a similar check after the machine select screen. It looks for Z+Up+A being held. If it is, it sets the “game mode” (at 0602ce60 ) to 9 , which is for the debug screen.

I looked for a way to unlock the extra mech with a cheat code, but didn’t find one. You should be able to do it with this Action Replay code, however:

The character select handling function (at 060ad404 ) checks the value at 0602b354 to see whether it’s greater than 2. If it is, it sets the mech limit to 7; otherwise it keeps it at 6.

Outro

For more on Planet Joker, see Peter Malek’s #BestOfSaturn article here at SHIRO!. And for more Saturn hacks and cheats from me, see our archive .

I’ll be back with more from the Saturn data mines next week! You can check out my Rings of Saturn blog on Substack if you’d like to see what else is going on in the world of retro game reverse engineering.

	Bo Bayles
		Rings of Saturn: 32bits.substack.com