# RetroCart emulator bundle

EmulatorJS **4.2.3**, with its matching legacy (WebGL 1, single-threaded)
cartridge cores. All runtime downloads come from this directory; ROMs are
passed as browser File objects and never uploaded. The frontend is adapted by
`app/javascript/retro_player.js` in a separate same-origin document. Destroying
that document stops the previous emulator before another cartridge starts.

Upstream: https://github.com/EmulatorJS/EmulatorJS/tree/v4.2.3
API reference: https://emulatorjs.org/docs/options/

`4.2.3/sources.json` records each downloaded URL and SHA-256. Rebuild with
`python tools/bundle_retro_emulator.py`. The upstream frontend is unmodified;
the adapter disables its localhost-only update check. The page's policy also
prevents remote fallback downloads. No BIOS images or games are bundled.

The frontend's GPL-3.0 license is in `4.2.3/LICENSE`. Each core archive contains
its upstream `license.txt`, `core.json` (including the source repository), and
`build.json`; the licenses are also extracted alongside the archives:

| System | Core | Source |
| --- | --- | --- |
| NES | FCEUmm | https://github.com/EmulatorJS/libretro-fceumm |
| Game Boy / Color | Gambatte | https://github.com/EmulatorJS/gambatte-libretro |
| Game Boy Advance | mGBA | https://github.com/EmulatorJS/mgba |
| SNES | Snes9x | https://github.com/EmulatorJS/snes9x |
| Mega Drive / Genesis | Genesis Plus GX | https://github.com/EmulatorJS/Genesis-Plus-GX |

Only these cores are hosted. Archives must be extracted by the player before
loading; ambiguous .bin files need a recognized cartridge signature. CHIP-8
has its own cabinet. Console compatibility remains that of the upstream cores.