Theming

'Theming' here refers to the theming of the test client. Fosscord can inject additional CSS into the client to allow you to change quite a lot about it's appearence.

There's three different CSS files injected into the client, in /assets/public, including fosscord-login.css, fosscord.css, and user.css. Fosscord developers may make changes to fosscord.css occasionally, so it's best to not touch this. user.css and fosscord.css are applied to all routes in the client, while fosscord-login.css is only applied to the login/register routes.

You can essentially throw any BetterDiscord/Replugged CSS theme into the user.css file and, given it was designed for the same client version, it'll work.