Examine source code of Blue Beyond

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#f0f0f0",
      "tab_background_text": "#dfe9f2"
    }
  },
  "version": "2.0",
  "name": "Blue Beyond",
  "manifest_version": 2,
  "description": "From the original game. I don't own the image used, I just adapted it to use it as a firefox theme."
}