Examine source code of neptune heart

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Neptune",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "left top"
      ],
      "additional_backgrounds_tiling": [
        "repeat-y"
      ]
    },
    "colors": {
      "toolbar": "rgba(87, 129, 145, 0.38)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(4, 19, 45)",
      "tab_background_text": "rgb(129, 191, 212)",
      "toolbar_field": "rgba(40, 81, 100, 0.43)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgba(255, 255, 255, 0.18)",
      "popup": "rgba(41, 135, 150, 0.61)",
      "popup_text": "rgb(255, 255, 255)",
      "popup_border": "rgba(41, 135, 150, 0.47)",
      "tab_loading": "rgba(255, 255, 255, 0.18)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6e3ea20b-7ab8-416b-bcae-bad0864db967}"
    }
  }
}