In this edition:

• Cotton Boomerang has a well-known cheat code that grants you extra options. I found that adding a couple of buttons to it unlocks more bonus items.
• Terra Cresta 3D also has a well-known cheat code that gives you extra lives. I found that it also enables a stage select function.

Two cheat codes that do more than the expected amount! Details are below…

Cotton Boomerang

It’s not well attested on English language websites, but you can unlock extras in Cotton Boomerang with a cheat code:

• At the Press Start Button screen, start holding X+Y+Z and keep them held.
• Then press and hold A and then B . Keep them held along with X+Y+Z .
• While still holding the other buttons, tap Start to bring up the mode select screen.
• Tap Down to highlight the Option item.
• Tap C to select it.
• Release the buttons you’ve been holding.

If you got it right, you’ll see Training mode as an option on the main menu. Free Play and Sound will also be added to the Option screen:

This is reported on a few Japanese cheat sites (like this one ). But I found something else: if you also hold L+R , you unlock the extra pictures in the art gallery!

Specifically, hold L+R+X+Y+Z at the title screen. Add in A and then B . Keep them held while tapping Start to bring up the main menu, Down to select Options, and C to open Options.

Technical details : The way this game handles input is fairly unusual (it’s the same as Cotton 2 , though). Most games store a bit pattern that represents which button is being held down somewhere in memory. Then they check that location against each pattern that’s associated with an action on the current screen.

Cotton Boomerang does this instead: it associates each button with a “time since last pressed” value. When a particular button is being left alone, its timer counts down from zero and gets increasingly negative. While it’s being pressed, it resets to zero and starts counting up. To perform actions, the game looks at these timers to determine which buttons have been pressed recently enough to be associated with actions.

For the cheat code above, Cotton Boomerang checks the timers for the X, Y, and Z to see whether they’re non-negative (i.e., currently being held). Then it checks to see whether A, B, and C’s values are consistent with them being pressed in the right sequence. If all of those conditions pass:

• 0604eed4 is set to 02 . This enables the extra options in the menu.
• 0604eed5 is set to 01 . This enables Training mode.

The game then checks to see whether L’s and R’s timers are positive. If they are, bits on the flag fields starting at 0604eed7 get set. These bit flips enable extra Gallery images.

Expressed as Action Replay codes, these effects are:

Terra Cresta 3D

Some Japanese cheat sites (like this one ) have a “99 lives” code for Terra Cresta 3D . On the mode select screen, enter this sequence:

You’ll see the Continue option pop up if you got it right:

Less well known is that after entering this code, you can press Y to change your starting stage:

When you begin, you will indeed have 99 lives:

Technical details : The function at 06024470 handles input on the mode select screen. It sets the cheat value at 0605026c to 00000001 if you enter the sequence above.

That value is read on the continue screen’s input handler (the function at 06024a18 ), which has logic like this:

Outro

For many more articles on Saturn archaeology, see my archive here at SHIRO!. And for even more retro game reverse engineering stuff, see my Rings of Saturn blog on Substack. I’ll be back next week with more!

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