The smallest theme.json

Create theme.json with this:

{
  "id": "ejemplo",
  "name": "Mi primer tema",
  "version": "1.0.0",
  "author": "Tu nombre",
  "description": "Rejilla de carátulas con ficha de juego (el tema de la guía)",
  "sdk": 1
}

Field	What it is
`id`	Required. A unique identifier: letters, numbers, `-` and `_` (64 at most). Do not use a built-in theme’s (`steam`, `ps5`, `xbox`, `switch`, `cinema`, `retro`, `moneda`). It usually matches the folder name.
`name`	Required. The name shown in the gallery.
`version`, `author`, `description`	Optional. The description appears under the name in the gallery.
`sdk`	The SDK version your theme uses. Today it is `1`.

There are more fields (entry, palette, host, sounds, settings…) that we will add in steps 7 and 8. entry is the entry page and, if you leave it out, it is index.html.

Not in the gallery? It is almost always badly written JSON (a trailing comma, missing quotes) or an id with spaces or accents. ejGames skips the theme and writes it to %APPDATA%\ejGames\logs\ejgames.log, on a line like WARN ejgames_lib::themes: tema C:\…\themes\ejemplo: trailing comma at line 1 column 33. Fix it and open Appearance again.

Themes

Step by step

The smallest theme.json