Tip: Layer 3 backgrounds and tides disappear when you hit a message box, so plan your level around that. For example, you can add a sublevel without layer 3 at the start/midpoint, and include your message there.
So, er, I was messing around with the titlescreen, and I decided to look through the layer 3 graphics. I looked at 192, 195, 198 and 1AD, which most people would've seen - they are oddly drawn tiles that don't really fit in with anything. I decided to put them in, and ordered them, until they looked like this:
What do those look like? I'll give you a clue: cap.
The upper 3 tiles resemble Luigi's (somewhat thinner) cap from side on, while the the lower tile resembles presumably Mario's cap from 45 degrees from his left. Interesting, huh? These look like they would fit on the titlescreen, but no other graphics remain of it, and the known beta titlescreen is quite different. Perhaps this is older than the above, or possibly something that was made for A titlescreen, but ended up unused, and were hence largely overwritten? The graphics are the same in the japanese release, unlike most unused layer 3 graphics… these are quite odd.
The RAM map says that storing $18 to address $9C has an unknown purpose, but it sets the item memory bit. SMWDisC says it generates tile 125, the one with the wings in it. Actually, I've found out what it does. It's used by the Yoshi coin to generate tile 25 below itself, but it doesn't set the high byte properly. Tiles not on the first page will generate 25, but the Yoshi coin will generate tile 125.
How is this helpful? It's not really, but it is helpful indirectly on one occasion. If you make the hex edit to make only the top half of a Dragon coin display, upon collecting the coin, it'll still delete the tile under it. However, armed with this knowledge, you can fix this:
This will change the $18 to a $01, fixing the issue.
Location: Montana, USA
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Yeah, the code for $9C setting 18 starts at $00C1AC. That's actually one of the things the Yoshi coin bugfix patch I made does; it makes the coin just use value 01 twice instead of using value 18, which causes the coin to always generate tile 25 even when it's on a Map16 page other than 0.
This is just a theory, but I think sprites 62 and 65 are incompatible because they store their # to an address somewhere that I think relates to automatic line-guided sprites. How could this be checked though?
-------------------- Let's milk Sunny Milk. Then she'll have enough money to fund Sunny Milk Real Estate.
Everypony's digging with a shovel