I am also unable to run in firefox (tested with a fresh, empty profile, no addons, in Firefox Dev Edition 135.0b2). After clicking "Run game", the new window opens and starts loading, but eventually fails with `Error: can't access property "fg", w is undefined` on the loading screen. Clicking "Try anyway" doesn't fix the error.
Based on the stack trace from the console (pasted at the end of this comment), and some poking around, it looks like your "Unknown color in blueprint" check is erroring when checking for a foreground color (w = w.fg) when w is undefined because the array of blueprint colors(?) doesn't contain an entry for '255, 255, 254' at all, so w is undefined.
i'm not 100% sure, since i'm working from the minified source, but it looks like, for some reason, firefox is getting different rgb values from the ImageData of menu_blueprint.png
Error getting store: TypeError: can't access property "fg", w is undefined https://html.itch.zone/html/12424542/2025-01-05/js/bundle.js:2:1058105 a bundle.js:2 F_ bundle.js:2 o bundle.js:2 a bundle.js:2 a bundle.js:2 L_ bundle.js:2 L_ bundle.js:2 (anonymous) bundle.js:2 a bundle.js:2 a bundle.js:2 o bundle.js:2 promise callback*l bundle.js:2 o bundle.js:2 promise callback*l bundle.js:2 N_ bundle.js:2 N_ bundle.js:2 (anonymous) bundle.js:2 (anonymous) bundle.js:2 (anonymous) bundle.js:2 (anonymous) bundle.js:2 a bundle.js:2 a bundle.js:2 a bundle.js:2 (Async: promise callback) l bundle.js:2 o bundle.js:2 (Async: promise callback) l bundle.js:2 o bundle.js:2 (Async: promise callback) l bundle.js:2 N_ bundle.js:2 N_ bundle.js:2 (anonymous) bundle.js:2 (anonymous) bundle.js:2 (anonymous) bundle.js:2