kinda wish there was a patch for all the Sonic games where it was applicable so that you cannot collect the rings you drop when you are hit, just like in the Master System games. Always felt like just being able to pick your rings back up removes any need to be cautious once you get at least one and makes the games to easy. That being said I still want a visual of the rings being knocked out of you, as it really helps as a visual indicator that you've taken damage.
That could be something you could make as a cheat.
The rings vanish fairly shortly after being hit so there is presumably a small timer in there somewhere. Find this timer and force it to be 0 or whatever gives you a fractional amount of time.
Finding timers is one of the less fun things in cheat making but should be possible to give yourself infinite rings and back yourself into a corner to continually be hit by a throwing enemy or something -- you might even want to bust out a level editor to make such a setup. At that point you have a reasonably steady thing to look at that controls for other variables. You could also try with a savestate made just as you get hit and then restored (presumably restoring the number). If the enemy thing is not going to work for you go somewhere quiet in a level and jump on some spikes.
Do note some timers count upwards so don't always use the "has decreased" option in your searches, or at leas if you are going to try that one at first if it is not coming up with good results then shift to has changed type searches.
If there is some kind of hard mode/easy mode in one of the games that speeds this up then so much the better.
If you are doing it the big boy hacker way then the thing will be on screen for a while. Find what is controlling it in the graphics department (should just be a matter of watching the sprite location memory) and trace it back up from there. Anything causing it to flash as they start to vanish will also be interacting with the timer at some level.
Minor idea (and I bet it could be done with AR codes but I lack the skills atm) but I'd love a hack/patch/code that prevented EXP gain in the GBAvanias (Circle of the Moon, Harmony of Dissonance and Aria of Sorrow).
In Aria of Sorrow, I managed to find (and edit) the memory bit related to the level, thus taking it to 255 and making a "level 1/no exp" run possible (and it's as fun as it's frustrating lol). I'd love to the same with said other games so if anyone can help I'd be grateful.
That should be fairly basic cheat searching effort. Find something that gives you experience (maybe just the one so some really basic enemy, are there any infinite zombies locations in these games?) and do a cheat finding session looking for changes. Give yourself infinite health and a shiny sword if you really want/need it.https://web.archive.org/web/20080309104350/http://etk.scener.org/?op=tutorial
That said there are already codes made for thingshttps://www.almarsguides.com/retro/walkthroughs/GBA/games/CastlevaniaCircleofTheMoon/ActionReplay/
Might need a copy of arcrypt, cbacrypt or whatever to allow you to edit the cheats but should be easy to force low what they force high.
Could also force your stats down to level 1 stats rather than max which would achieve much the same effect.https://megalixir.cc/gba/castlevania-harmony-of-dissonance/https://megalixir.cc/gba/castlevania-aria-of-sorrow/http://bsfree.org/hack/hacking_gba.html
for how the unencrypted codes work (and the tools page should have the downloads if they are not otherwise available). The GBA does have some nice options here as far as less than, equal to and the like codes.
If you want to hardpatch them into a game to play on a flash cart or emulator with iffy cheat support (or simply don't want the hassle) have a look for GBAATM. There is a modern port/remake as well https://gbatemp.net/threads/gbaatm-rebirth-gba-auto-trainer-maker-a-new-hope.564321/