Nice work. What did you end up having to do to get the feature working? That's a feature that really should have been part of the original game.
It was surprisingly straightforward. There's more than enough free ROM space as well as save-RAM. I'm working on some other modifications that sound as if they would be simpler, but are turning out to be much more difficult (for example, making the subscreen open and close faster sounded so simple, but it's glitches galore).
So it's an actual hack and not a LUA script like that thing for Metroid?
Yup. There are two Metroid mods that provided a map. Parasyte hacked in a map that somewhat resembled Super Metroid's corner map. It was a 3x3 grid that simply showed whether there were any adjacent screens. Wasn't mind blowing, but it would presumably run on real hardware. MDBtroid had the LUA map that was more akin to Super Metroid's map in the pause screen.
Jigglysaint, I added my own map data using free save-RAM. I'm guessing that there's a bit field for every map (overworld, levels 1-6, levels 7-9), but that it would be used to track visited screens in levels and revealed secrets in the overworld. That's just a guess, though.
Worth mentioning: there are a number of random bits in the overworld data that, if they are changed, adversely affect the game (for example, there are two screens where changing the screen palettes affects which palettes are used in caves). I wonder what issues might crop up if you redo the whole map system. Also, there are plenty of simple hacks that could expand what options you have for screens. For example, it would be very easy to re-point the lists for which screens have armos-staircases, whistle stairs, etc., to give you virtually free reign. One thing I could never figure out is how the raft screens are managed. If I were more adept at ASM-hacking when I made Zelda Tech, I would have provided the user an option to "enhance" the game to provide more of these liberties.
Tito Santana, I'll PM you a link to the IPS. If you know anyone else who might be interested, you can share the link (just don't post it publicly). If anyone else wants to test, whether it's a full play-through or something less, please PM me. (Please