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Generation I Glitch Discussion

Moving Q: Appears as Map Corruption? Debug Yellow - Page 1

Moving Q: Appears as Map Corruption? Debug Yellow

Posted by: 44HyXpert
Date: 2017-11-22 10:52:54
I was messing with TheZZAZZGlitch's Debug Yellow (https://www.youtube.com/watch?v=BkIDPwkeGWs) when I discovered an odd effect from moving a Q to the front of the party.

The Q in question is actually rather specific, obtained by changing $D162 to be larger than your current team. The result is a Q with a species identifier of FF and everything else at 00. Changing $D162 also does not cause memory corruption on its own, as the "real Q" that keeps the party stable moves down and duplicates / stays in its previous spot.

I wanted to see the game's reaction to having an empty Q duplicated from the "real Q" in the front of the party, with another Pokemon behind it. I thought the only possibilities were blacking out or continuing on, but it actually did neither (and didn't crash, either!).

When I moved the Q to the front of the team, I was able to move around, but the game acted almost as if a map corruption had taken place. Any area off-screen was loaded as glitchy tiles and text, and it filled the background when the start menu was opened, but remained the same underneath. (Upon trying this again, I noticed the game would, at this point, turn off all colliders) Eventually, after 4 steps, the game locked me in a closed tile, not allowing me to move any further, but I was able to collide with the walls around me and I could open the menu, allowing me to enter a battle (by $D058). In the battle, the game showed Q as fainted and I sent out the second Pokemon. After exiting the battle, the game returned to normal, with this effect happening again if I moved 4 steps.
Why does this happen?

Re: Moving Q: Appears as Map Corruption? Debug Yellow

Posted by: ISSOtm
Date: 2017-11-22 12:12:37
It's not duplicated from the "real Q", it's the game interpreting unrelated data as a Pokémon.
In which slot was the Q prior to swapping ?

Anyways, independently of the answer to the above question (which is still important), what happened is that you corrupted the tile block pointer, and probably your coordinates also. As for the four-step corruption, I don't know.

Re: Moving Q: Appears as Map Corruption? Debug Yellow

Posted by: Stackout
Date: 2017-11-22 14:11:26
the 4-step thing reminds me of the (international) dokokashira door glitch - doesn't it have a similar cause?

Re: Moving Q: Appears as Map Corruption? Debug Yellow

Posted by: Couldntthinkofaname
Date: 2017-11-22 14:13:55
A somewhat similar cause. In Dokashira door, the end terminator is placed before the game's expectations, causing a very large Pokémon menu. Since one of the "Pokémon" are considered poisoned, an address somewhere is constantly being decremented upon taking 4 steps.

This is probably what's happening here, an address is being decremented somewhere. Q is considered an end terminator due to it being Hex $FF.

Re: Moving Q: Appears as Map Corruption? Debug Yellow

Posted by: 44HyXpert
Date: 2017-11-22 15:41:21

It's not duplicated from the "real Q", it's the game interpreting unrelated data as a Pokémon.
In which slot was the Q prior to swapping ?

Anyways, independently of the answer to the above question (which is still important), what happened is that you corrupted the tile block pointer, and probably your coordinates also. As for the four-step corruption, I don't know.


The Q was in the second slot.
You were right, I looked at the list again, and it gave effects similar to Dokokashira. **changing $D162 does give similar effects to Dokokashira, but in this case, there was no poisoning, lag, long party list, or anything else to suggest the party was in an unstable state, which really confused me. The team is in a stable state when this happens (because of the second Q which always forms under the first Q).
There's also a few other things, like the party list in battle only showing two active Pokemon- the fainted Q and my second Pokemon- and the fact that the game restored my coordinates to normal after I exited the battle.

Re: Moving Q: Appears as Map Corruption? Debug Yellow

Posted by: 44HyXpert
Date: 2017-11-22 15:48:42

A somewhat similar cause. In Dokashira door, the end terminator is placed before the game's expectations, causing a very large Pokémon menu. Since one of the "Pokémon" are considered poisoned, an address somewhere is constantly being decremented upon taking 4 steps.

This is probably what's happening here, an address is being decremented somewhere. Q is considered an end terminator due to it being Hex $FF.


I think it's probably something similar, although I don't think it's from poison, as I've never seen the poison flashing effect from it. It seems like two areas of the game are conflicting somehow. Sort of like the game's reaction to Q in a fusion / hybridization: In battle, a Q is completely useable and shows up as active on the party list; but when viewed by the PC, it is registered as just a stopping point.