Firehawke's Stream of Consciousness

My luck never ceases to be trying to knife me in the back. Managed to get a slight stomach bug that’s throwing my concentration out the window. I’m feeling pretty drained, and I don’t feel like I managed to really get anything useful done code-wise in-between naps.

I did, however, get a chance to look at Metroid’s use of WRAM a little better. I feel like this Lua project is helping me understand the Metroid code a lot better. The port from Famicom Disk System had to have been a bit of a challenge, as the original code made definite use of extra RAM the FDS added, forcing the use of extra RAM in the cartridge itself.

What I wasn’t quite expecting is that apparently not all that RAM is being used by the game itself. There’s apparently quite a bit of free space! The Lua script uses a chunk of that free space at the end of the WRAM mapping space for keeping track of the map, as I’d previously stated in my last post. After doing a bit of digging, I was able to find a good location (read: not being touched by the existing script or by the game itself) to store configuration settings for the script.

While doing the initial research in this area, I learned something very interesting. Zelda, also itself an FDS port, needed similar treatment in the conversion to cartridge: There they also use a significant chunk of the WRAM for holding a code bank, and a very tiny amount for the actual saved games. Mario 2, also a (heavily modified) FDS conversion, also used WRAM in the prototype phases. By the time the game was done, though, they’d converted it to a different mapper.

Any case, I’ve made a bit of progress, but I don’t have anything tangible to show for it because I’m having trouble keeping focus on code. Hopefully I can get back on track for that part soon, but in the meantime I’ll just keep working on what I can. The better my understanding of this, the easier it will be in the long run.

I’ve been doing some deep digging into the depths of the original Metroid the last few days, as a result of getting sudden inspiration from Neill Corlett’s Lua script for Metroid under FCEUX.

I’ve found more incompatibilities with the script and semi-recent builds of FCEUX since I reported the initial bug to him, and I’ve been cleaning things up as I go. FCEUX seems to have changed some Lua functions in backwards-incompatible ways.

As a result, I’ve actually had to keep the original script website open on a secondary monitor while working on the script, in order to see how he intended it to actually look, because FCEUX’s most recent stable build as of now breaks the look a LOT worse than I’d expected.

I could have sworn it was possible through a password hack to get an ice beam with the wave properties, but I haven’t been able to reproduce it. Maybe my memory is faulty. I’ll keep looking at that one, but I’ve got a lot of other stuff to be digging through as well.

For instance, I’ve added a third screen to the script for configuration of individual features. This came from RetroNutcase’s comment that he wouldn’t want the destroyed block timers. I haven’t yet added the ability to toggle specific script features just yet, but that’s next on my list of things to be looking at.

I should also see if there’s any way to save a text config file to the current directory (hopefully where the script itself is stored?) for a platform agnostic way to save settings for the script. Actually, I just realized he’s probably saving the map info to NES RAM so to be able to save it as part of a savestate. That suddenly makes this all make a lot more sense. Instead of using a config file, I should use NES RAM if there’s any free—I’ll need to actually look at the memory map.

This is actually the first Lua scripting I’ve actually done any serious work with, so I’m also learning as I go. This also makes the going a bit slower than I’d prefer, but you can’t win them all.