src/index.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>webpack App</title>
    <style>
      .web-clipper-loading {
        position: fixed;
        right: 10px;
        top: 10px;
        box-shadow: rgba(0, 0, 0, 0.2) 0px 0px 12px 0px;
        background: white;
        width: 324px;
        height: 150px;
        display: flex;
        align-items: center;
        justify-content: center;
      }

      .web-clipper-loading .line {
        animation: expand 1s ease-in-out infinite;
        border-radius: 10px;
        display: inline-block;
        transform-origin: center center;
        margin: 0 3px;
        width: 1px;
        height: 25px;
      }

      .web-clipper-loading .line:nth-child(1) {
        background: #27ae60;
      }

      .web-clipper-loading .line:nth-child(2) {
        animation-delay: 180ms;
        background: #f1c40f;
      }

      .web-clipper-loading .line:nth-child(3) {
        animation-delay: 360ms;
        background: #e67e22;
      }

      .web-clipper-loading .line:nth-child(4) {
        animation-delay: 540ms;
        background: #2980b9;
      }

      @keyframes expand {
        0% {
          transform: scale(1);
        }
        25% {
          transform: scale(2);
        }
      }
    </style>
  </head>
  <body>
    <div id="app">
      <div class="web-clipper-loading">
        <div>
          <div class="line"></div>
          <div class="line"></div>
          <div class="line"></div>
          <div class="line"></div>
        </div>
      </div>
    </div>
    <script type="text/javascript" src="vendor.js"></script>
  </body>
</html>