<!DOCTYPE html>
<html>
  <head>
    <style>
      body.scrollable {
        width: 200lvw;
        height: 200lvh;
      }

      div {
        width: 200px;
        height: 200px;
        background-color: skyblue;
      }

      ::view-transition-new(*) {
        animation-duration: 30s;
        opacity: 0;
      }
      ::view-transition-old(*) {
        animation: unset;
        opacity: 1;
      }
      */
    </style>
    <script>
      function startTransition() {
        window.transition = document.startViewTransition(() => {
          document.body.classList.toggle('scrollable');
        });
      }

      onload = () => {
        const params = new URLSearchParams(window.location.search);
        if (params.has('scrollbar')) {
          document.body.classList.add('scrollable');
        }
      }
    </script>
  </head>
  <body>
    <div></div>
  </body>
</html>
