Examine source code of Dr. Mario NES

{
  "name": "Dr. Mario NES",
  "manifest_version": 2,
  "version": "5.0",
  "theme": {
    "images": {
      "theme_frame": "firefox theme.png"
    },
    "colors": {
      "frame": "rgba(255, 255, 255, 0)",
      "tab_background_text": "rgba(190, 192, 49, 1)",
      "toolbar": "rgba(255, 255, 255, 0)",
      "bookmark_text": "rgba(190, 192, 49, 1)",
      "toolbar_field": "rgba(255, 255, 255, 0.55)",
      "toolbar_field_text": "rgba(0, 0, 0, 1)",
      "tab_line": "rgba(190, 192, 49, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{7276f532-af6d-491f-a77b-655d5eacb501}"
    }
  }
}