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A theme is a complete web page (HTML + CSS + JavaScript) that draws your library however you want. Nothing needs compiling: you save, and it reloads. The house theme (Moneda) and the platform themes in the repository’s themes/ folder (Steam, PS5, Xbox, Switch, Cinema and Retro, switched off in the app for now) are built with exactly what this guide explains. Use them as examples.

Step-by-step guide

Your first theme from scratch: a cover grid, a controller, a game page and options that need no code.

Reference

theme.json, the full window.ejg SDK (including Explore and Downloads) and the utility kit.

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Start in 1 minute

1

Pick a base

Settings → Appearance → the theme closest to what you want.
2

Duplicate it

Press Duplicate to edit. It is copied to your themes folder (%APPDATA%\ejGames\themes\<id>-custom) and becomes the selected theme.
3

Open its folder

Turn on Developer mode (same screen) and press Open theme folder.
4

Edit

Change style.css or main.js in your editor. On save, the theme reloads by itself.
F5 reloads the theme by hand. If the theme hangs (it does not answer within a few seconds), ejGames falls back to the house theme, Moneda. A JavaScript error does not switch themes: it leaves the theme blank and, with developer mode on, shows up as a notice. Hold Shift while opening ejGames to start in safe mode. The gallery reads the themes folder again each time you open Appearance, and theme.json changes apply when the theme reloads. You do not need to restart.

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Layout

  • theme.json names the theme, lists the options it offers in Appearance, and sets the colors the launcher screens use.
  • window.ejg is the SDK: the library, launching games, the controller, achievements, downloads…
  • The kit (/_sdk/kit/) has what almost every theme needs: controller navigation, art that fits, formatters, trailers.
The finished example from the guide is in examples/ejemplo-tema/.