third_party/blink/web_tests/external/wpt/scroll-animations/css/at-scroll-timeline-default-descriptors-ref.html

<!DOCTYPE html>
<title>Reference for default @scroll-timeline</title>
<style>
  html {
    min-height: 100%;
    padding-bottom: 100px;
  }

  #box {
    width: 100px;
    height: 100px;
    background-color: green;
    transform: translateY(100px);
  }

  * {
    margin-top: 0px;
    margin-bottom: 0px;
  }
</style>

<div id="box"></div>

<script>
  window.addEventListener('load', function() {
    // Move the scroller to halfway.
    const scroller = document.scrollingElement;
    const maxScroll = scroller.scrollHeight - scroller.clientHeight;
    scroller.scrollTop = 0.5 * maxScroll;
  });
</script>