Examine source code of Gravity01

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Gravity",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "left center"
      ],
      "additional_backgrounds_tiling": [
        "no-repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(37, 26, 12)",
      "toolbar_text": "rgb(187, 202, 202)",
      "frame": "rgb(0, 0, 0)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(93, 93, 102)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(247, 246, 244)",
      "popup": "rgb(17, 11, 1)",
      "popup_text": "rgb(79, 108, 185)",
      "tab_loading": "rgb(247, 246, 244)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{04cefced-7a1c-415d-9b10-bb2b0e70e814}"
    }
  }
}