-between;
      }
    </style>

    <!--
      - JavaScript and HTML must be in separate files: see our Content Security
      - Policy documentation[1] for details and explanation.
      -
      - [1]: https://developer.chrome.com/extensions/contentSecurityPolicy
    -->
    <script src="browser-polyfill.min.js"></script>
    <script src="popup.js"></script>
  </head>

  <body>
    <h1>Background Color Changer</h1>
    <div id="container">
      <span>Choose a color</span>
      <select id="dropdown">
    