replayed Castlevania Symphony of the Night yesterday in what is at this point an almost-yearly tradition, and afterwards went a-websearching to see if there is an open source reverse engineering of the game yet. it looks like there now is, but it's in the style of the various recentish N64 decompilation projects and is making slow progress, somewhat understandably.
i'm very spoiled in this regard on Doom et al where we have PC-based C/C++ source that's been ported to everything, is now mature, has had a cool scripting + modding layer added, etc. so it'll probably be a good few years before anything like that happens. but SotN is on my list of games that are significant and/or interesting enough to merit that level of preservation (alongside Rez and Katamari Damacy; and several others than have actually now gotten that treatment).
i also came across this nifty level editor, which is also still in early stages but it's a thrill to be able to see the raw level data rendered nicely with some familiar imgui-based editor UI for poking around it.
got the editor working on my system - nifty! i'm always kinda impressed when flip-screen games take the trouble to actually match up screen edge geo exactly when they don't technically need to do that, but it probably simplifies the screen transition logic pretty radically. (and it looks like the vertical transitions have 32px of padding...)