Keyboard-accessible scrollbox

<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">

<title>My code example</title>
<style>
:root {
  font-family: system-ui, sans-serif;
  color: #18223b;
}
* {
  box-sizing: border-box;
}
body {
  margin: 0;
  min-height: 100vh;
  padding: 24px;
  background: #edf1ff;
  display: grid;
  place-items: center;
}
main {
  min-width: 0;
  width: min(100%, 600px);
  background: white;
  border-radius: 20px;
  padding: clamp(20px, 5vw, 32px);
}
h1 {
  font-size: clamp(24px, 5vw, 32px);
  line-height: 1.2;
  margin: 0 0 16px;
}
h2 {
  font-size: 20px;
  margin: 24px 0 12px;
}
p,
li {
  line-height: 1.65;
}
a {
  color: #2545a8;
  text-underline-offset: 3px;
}
button,
input,
select,
textarea {
  font: inherit;
}
button {
  min-height: 44px;
  border: 1px solid #9eaed0;
  border-radius: 10px;
  padding: 10px 14px;
  background: #eff3ff;
  color: #18223b;
  cursor: pointer;
}
a:focus-visible,
button:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible,
[tabindex]:focus-visible {
  outline: 3px solid #3658bf;
  outline-offset: 3px;
}
pre {
  max-width: 100%;
  overflow: auto;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
  background: #eef2fa;
  padding: 16px;
  border-radius: 10px;
}
code {
  font-family: ui-monospace, monospace;
}
.scrollbox {
  max-height: 220px;
  overflow: auto;
  overscroll-behavior: auto;
  border: 1px solid #9eaed0;
  border-radius: 12px;
  padding: 20px;
  scrollbar-gutter: stable;
}
.scrollbox h2 {
  margin-top: 0;
}
</style>
</head>
<body>
<main
  >
  <h1>A scrollbox you can use with a keyboard</h1>
  <p
    id="scroll-help"
    >Focus the reading box, then use the arrow keys, Page Down or Page Up. The surrounding page still scrolls normally.</p
  >
  <section
    class="scrollbox"
    tabindex="0"
    role="region"
    aria-label="A short reading list"
    aria-describedby="scroll-help"
    >
    <h2>Small steps for a useful page</h2>
    <p>1. Give the page one clear purpose and a descriptive main heading.</p>
    <p>2. Use paragraphs and lists to make the content easy to scan.</p>
    <p>3. Choose links that describe their destinations.</p>
    <p>4. Keep text readable at different screen widths.</p>
    <p>5. Test the page with a keyboard as well as a pointer.</p>
    <p>6. Respect reduced-motion preferences when adding animation.</p>
    <p>7. Open the copied file and check that it works without missing assets.</p>
    <p>8. Keep short text on the page when a nested scrollbox is unnecessary.</p>
  </section
  >
</main
>
<script>

</script>
</body>
</html>