<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Overflow: ::scroll-button on root element</title>
<style>
  body {
    margin: 0;
  }

  .item {
    width: 600px;
    height: 300px;
    margin-bottom: 20px;
    background: green;
  }
</style>
<button style="position: absolute;">down</button>
<div id="first" class="item"></div>
<div class="item"></div>
<div class="item"></div>