Atari 2600 → C64 builder

A web page that turns your own Atari 2600 cartridge ROMs into Commodore 64 versions (.prg and .d64), and lets porters make profiles for their own C64 ports. Everything runs in the browser; nothing is uploaded.

index.html is the whole tool in one file:

• On the website it reads games/index.json and lists those games: drop a ROM (or its .zip) and download the C64 version. Games not listed work too: drop the ROM together with the game's profile (.json).
• Saved to disk and opened on its own (the page has a "Download this page" link) it works standalone: drop each ROM together with its profile. Browsers don't let a page opened from disk read other files, so offline it always works this way.
• Make a profile (second tab, or index.html#make): drop a finished C64 port (.prg) and the ROM it was made from; the details are filled in from the .prg's BASIC lines; download the profile. It's refused unless it rebuilds the .prg byte for byte and the ROM clearly matches.

This folder contains no original game code. Each profile in games/ is a plain JSON data file holding a port's C64 program with every byte of the original ROM blanked out, plus a list of where those bytes go back; the user's ROM, checked by MD5, fills them in. Profiles are only ever read and checked as data, never run, so they're safe to share and to accept from anyone.

Files

File	What
index.html	the tool (generated by the maintainer's tools/mkpage.js; don't edit by hand)
games/index.json	the list of this site's profiles
games/<id>.json	one profile per game

Adding a game to the site

Put its profile in games/ and add it to games/index.json (the maintainer's publish.cmd does both the list and the publishing).

Hosting on GitHub Pages

Put the contents of this folder at the root of a public repository, then in the repository's Settings → Pages choose Deploy from a branch, branch main, folder / (root).