Are these cores possible/in the works?

JamesMcK: sounds like a cool project. You can write it in pretty much any language you like, but if you want it to compile on all of the platforms RetroArch supports, C or C++98 (or earlier) are best.

If you need help getting started or just have any questions, come to #libretro on Freenode IRC.

I know this is a very old post, but were you able to do that, or any idea if there is a way to get ZSNES uploaded as a core? I know I’ve used that for what feels like since day one, but I needed a better platform for all of my other roms, hence why I got onboard RA.