Examine source code of Rain world

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Rain world",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right bottom"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(0, 0, 0)",
      "toolbar_text": "rgb(134, 187, 255)",
      "frame": "rgb(0, 0, 0)",
      "tab_background_text": "rgb(170, 211, 255)",
      "toolbar_field": "rgb(255, 255, 255)",
      "toolbar_field_text": "rgb(0, 37, 82)",
      "tab_line": "rgb(29, 29, 29)",
      "popup": "rgb(44, 50, 101)",
      "popup_text": "rgb(0, 115, 255)",
      "icons": "rgb(249, 247, 255)",
      "ntp_background": "rgb(0, 0, 0)",
      "tab_loading": "rgb(29, 29, 29)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{3ded29a5-9a15-4d0f-811a-59005a66c9aa}"
    }
  }
}