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                <!-- loading画面 -->
<div id="js-loader" class="loader"></div>

  <p>Lorem ipsum, dolor sit amet consectetur adipisicing elit. Maxime voluptate mollitia assumenda eius illo eum eaque minima obcaecati culpa voluptas cumque beatae aut et fuga minus illum perspiciatis, inventore quidem.</p>


                .loader {
  align-items: center;
  background: #fff;
  bottom: 0;
  display: flex;
  justify-content: center;
  left: 0;
  position: fixed;
  right: 0;
  top: 0;
  z-index: 999;
  &::after {
    animation: loader 0.5s linear infinite;
    border: 1px solid orange;
    border-radius: 50%;
    border-right: 1px solid rgba(orange, 0.2);
    border-top: 1px solid rgba(orange, 0.2);
    content: "";
    height: 70px;
    width: 70px;

@keyframes loader {
  0% {
    transform: rotate(0);

  100% {
    transform: rotate(360deg);

body {
  font-family: "Helvetica Neue", Arial, "Hiragino Kaku Gothic ProN", Meiryo, sans-serif;

  line-height: 1.6;
  max-width: 500px;
  margin: 0 auto;
  padding: 25px;
    font-size: 32px;
    font-weight: bold;
    font-size: 16px;
    margin-top: 30px;


                const loader = document.getElementById('js-loader');
window.addEventListener('load', () => {
  const ms = 400; = 'opacity ' + ms + 'ms';
  const loaderOpacity = function(){ = 0;
  const loaderDisplay = function(){ = 0;
  // setTimeout(loaderOpacity, 1);
  // setTimeout(loaderDisplay, ms);
  // デモ用
  setTimeout(loaderOpacity, 5000);
  setTimeout(loaderDisplay, 5000 + ms);