I'm thinking about writing (or at least trying to write) an editor, and I first want to poke around the ROM to see if I understand the format. The problem is that I can't follow the website. I tried following this formula to convert the offset to an address, but I'm not getting any useful results, e.g. the location that's supposed to be "empty and filled with $FF" has no $FF anywhere near it.
Am I missing something? Am I doing it completely wrong?
Thanks.