This post by Sudden Desu (anyone know if he's a member here?) is worth a full read-through, so I won't go into the details here. What is relevant (to me!) is that it includes two Mame cheats I was interested in trying on actual hardware, one to enable Debug options, and another to turn the debug 'Program Menu' into a pointer to some unused code instead -- that code being a strange Dueling Cakes "Jikken Program". I thought I'd edit the program rom to enable both those things, to start, so here it is.
Patch original file 224-p1.p1 with the attached 224-p1.ips.
Path the multi file "prom" in the twinspri directory with prom.ips.
I use Lunar IPS: http://www.romhacking.net/utilities/240/
To play the Dueling Cakes game, you just hold down p2 A+B+C+D during the BIOS screen.
If I get ambitious I may look into making a more polished version of this, since having the debug flag enabled can interrupt actual Twinkle Star gameplay. I'm not sure if it's possible but it would be nice to enable/disable the various flags -- debug, this Jikken Program, etc. from some menu somewhere. That way you can play the game normally, or toggle this stuff too. But that'll take some real work as I have done zero 68k assembly so far. Maybe new menu guy wants to throw me some tips
Thankfully there seem to be a lot of resources out there already, so if I make any progress on that, I'll drop it here in this thread too.
Happy cake fighting
Patch original file 224-p1.p1 with the attached 224-p1.ips.
Path the multi file "prom" in the twinspri directory with prom.ips.
I use Lunar IPS: http://www.romhacking.net/utilities/240/
To play the Dueling Cakes game, you just hold down p2 A+B+C+D during the BIOS screen.
If I get ambitious I may look into making a more polished version of this, since having the debug flag enabled can interrupt actual Twinkle Star gameplay. I'm not sure if it's possible but it would be nice to enable/disable the various flags -- debug, this Jikken Program, etc. from some menu somewhere. That way you can play the game normally, or toggle this stuff too. But that'll take some real work as I have done zero 68k assembly so far. Maybe new menu guy wants to throw me some tips

Happy cake fighting