RosaTheRad

The .arc files are all audiovisual assets: UI elements, mostly. I'm having a hard time finding actual code.

Hold on. I made a breakthrough I think you'd be interested in. I found this thread on another site where a user provides a batch file for a decompression program. Using this, I turned BIRIZION.bcres.cx into Dec_BIRIZION.bcres.cx. At first I thought it didn't work, but when I opened the new file in a hex editor, I found legible text strings. So, I chopped the .cx extension off the file and opened it in Every File Explorer. The model and textures were there, and I exported them to Blender. I'm going to try this on the .arc files now.

You are not alone... I also want to hack the game's files. And just like you I saw the "no public tool exists for this yet" from 2015. My endgoal though is to mod shinies into the game like how they exist in Rumble (WiiWare). I found a script for a program called "quickBMS" that decompresses the .cx files in Rumble U (WiiU), but it throws errors when I try to use it on .cx files from Rumble Blast (3DS). Error: incomplete input file 0: C:\...\romfs\assault2d.arc.cx Can't read 476176 bytes from offset 0000bc04. Anyway don't worry, it's possible that the BMS script has been written to exit in this way if it's reached the end of the archive so check it or contact its author or verify that all the files have been extracted. Please check the following coverage information to know if it's ok. coverage file 0 99% 48120 48132 . offset 0000bc04 Last script line before the error or that produced the error: 12 clog NAME 20 ZSIZE SIZE - OFFSET 0x00000014 - ZSIZE 0x80000202 - SIZE 0x0e0000f5 coverage file 0 99% 48120 48132 . offset 0000bc04 If I'm using the program correctly (which I might not be, I've never modded a game before), this leads me to believe that perhaps the .cx compression algorithm used in the Rumble series is slightly different between entries, thus why this errors. Or, it could be that this script is searching for data that would only be found in Wii U game files that are different in 3DS game files. AbsolBlogsPokemon made the Rumble Weekend Edition mod, he'd probably be the most knowledgeable about how Rumble works, and by extension Rumble Blast. Rumble Blast ported its models, textures, music, sounds, moves, and species data straight from Rumble, so it wouldn't surprise me if the code of both games also had very similar internal structures. Unfortunately he's a busy guy with no contact info. He's on Twitter and BlueSky though, both of which I don't use and don't ever plan on using, so maybe someone else can poke him about it and try to convince him to share more of what he learned. I wish I could be of more help. I'm as clueless as you are.