I was going to do this game about a year ago but hit a road block immediately. Let me explain.
Most games are ridiculously easy to capture. I just find a couple memory locations (Map ID, Actor Position, Camera Position) and I can zip through the game in about a week. But, this game was unforgiving.
I found the address for the actor location pretty quick, so I started manipulating that to get around the scenes. But, I learned pretty quickly that this game was not like most. As soon as I moved to a tile that I wasn't supposed to be on, like the ones on the other side of walls, I would get ported out of the area and back to the world map. It was weird so I took a look in memory for a solution. I checked if I could just manipulate the camera directly, but that was a no go. I tried corrupting some of the surrounding memory it hopes of uncovering some secret bytes that let me move where ever I want. Nope.
So, I gave up on the game. It seemed as though it couldn't be captured. But, today I loaded it back up with the intention of finding a way to capture it. No matter what! After about eight or nine hours of trudging through memory byte-by-byte, I came upon a group of bytes that didn't seem to be of any use at first glance. This group of 8192 bytes starts at 9726h. After a few minutes of manipulating them, I noticed something quite interesting. Each byte was actually the ID of each tile for the current scene. This was amazing!
I quickly through together a program that could read the bytes and output the correct tiles in that order to create the entire scene. This worked, but only partway. It seems the first 4096 bytes of this block is used for BG2 while the second 4096 bytes are used for BG3. The were no bytes for BG1 or BG0. Very disappointing.
Then I had an idea. What if I just changed the ID of all the tiles to that of a walkable tile? It may work since the tiles don't get updated until the screen is refreshed via the status menu or scrolling. It worked somewhat, but as soon as I started scrolling the tiles refreshed and changed into the wrong ones. Ok, that's fine. What if I just change a couple tiles? Maybe just the tiles around me? That way they won't refresh until they scroll off-screen but that won't matter since I sill have already captured that portion of the scene. It worked! Yay!
So, about eleven hours total today got me the ability to capture this treacherous game. There were other minor things I found, such as a way to move my sprite off the screen so I can capture other important sprites. But, all in all it has been a long and rewarding adventure. I learned some new things about the game and about myself.
Memory Locations
9726 Tile Start
E2AE Map ID
E2B2 PosX
E2B3 PosY
E397 Set to zero to move sprite off-screen.
E398 Same as previous.
