Secret of Evermore Wings Glitch patch

Channel:

Master Knight DH

Subscribers:

1,950

Published on January 23, 2021 9:08:34 PM ● Video Link: https://www.youtube.com/watch?v=22tt9lb0KJE

Game:

Secret of Evermore (1995)

Duration: 2:36

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1

0:00 - Original
1:04 - Wings Patch

Wings Patch here:
https://drive.google.com/file/d/1ooSjc8soZuPgkOfEinbQ2S8EZeGQTxQd/view?usp=sharing
IMPORTANT NOTE: this only applies to the non-headered US ROM. Other versions of the game will shift the modified spell instruction accordingly and the European ROMs will additionally likely shift the instructions meant to be now called by the 2 added Jumps.

So yep, I'm back to datamining Secret of Evermore because real life issues are just too overbearing at this point for me to want to handle Link to the Past at the moment. Hey, if nothing else, I can get back to handling stuff with a game I thought I was done with, but apparently not. At least I don't have to worry about being called disloyal though.

For those wondering, the Wings Glitch is a glitch where the player becomes completely invincible and certain enemies don't attack them whenever the player uses Wings/Escape on a screen where the warping out won't happen, and retains this state indefinitely until they leave the screen and enter a new one. I decided to investigate what was happening because a flag that provided invulnerability kept bugging me and I suspect it did have something to do with Wings/Escape, and as I was checking things out around Halls of Collosia to test status handling, I noted how the Mad Monks still attacked the Dog but not the Boy, so I used Escape again and then somehow only the Boy but not the Dog took damage from the Plague that I got on BOTH characters.

Then I tested on a Rimsala in Omnitopia, and noted that the Wings Glitch wasn't active on an even number of Wings/Escape uses. This allowed me to find the culprit flag that would have been inverted by Wings/Escape fizzling: Character Offset $14 Bit 8, which turns out to be the flag for Mercy Invincibility for spell targets.

What happens is that the script for Wings/Escape has its success check either simply update to the next instruction byte of the process if Wings usage is valid, or it simply displays the failure message and immediately terminate the script immediately otherwise. The termination is done by a JMP to what turns out to be Spell Instruction $22 that is the standard ending, and this brings up that the process that inverts the Mercy Invincibility flag, Spell Instruction $36, is used twice for spell scripts in general: the first time to activate it, and the second time to deactivate it. Wings/Escape forgot to account for this, so effectively the Script uses it only ONCE during the failure. Adding to this, Spell Instructions tend to be called by JSRs and consequently end up with RTS endings, so I couldn't change the Program Bank at all when calling them, meaning no using PB $0F since the Spell Instructions are in PB $11. I had to figure something out.

Fortunately, as I expected, Spell Instruction $22 has the success branch use recycled coding, so I could change that entire branch to a JMP, funnily enough leading to the same coding at the end of Spell Instruction $36 (complete with the Set Carry), and that would be 7 more bytes of room, 3 of which I could expend on a JSR to the start of Spell Instruction $36. This video provides the results as displayed particularly by the Skelesnails' behavior. Funny thing is that Escape can be kept as a panic button of sorts in boss battles because it is at least more fair than Celestial Fireworks in Kid Icarus Uprising, not having intangibility last freaking 90 frames.

The best part is that I actually reduced the used up room on the ROM by making use of pre-existing code, so even if it's 4 bytes I save, I definitely avoided using surplus on this once elusive glitch. Kind of handy, that.

Oh, and yes, I intend to work on the 25th Anniversary Balance Patch, although at this point, that's an Artifact Title. It's something I can do and I would definitely appreciate corroborative efforts in the interest of supporting other ROM versions at the very least, in addition to getting useful fixes like balancing with choosing between having or not having the 2P patch implemented in mind and elaboration on the game's anti-piracy handling in case it's anything like what Earthbound uses. I also plan to make an actual changelog text file like what Bloons Tower Defense 6 does and keep the default version around for historical purposes. But yes, this mini-patch is at least a success. And if feasible, I'd be glad if this can be finished in a welcome timeframe, just so I can actually get to other things. Again, I'm still out in the open about my parents' house, so I don't want to work on Secret of Evermore forever.

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