<!doctype html>
<meta charset="utf-8">
<title>CSS Test Reference</title>
<style>
  summary {
    display: list-item;
    counter-increment: list-item 0;
    list-style: disclosure-closed inside;
  }
  details[open] > summary {
    list-style-type: disclosure-open;
  }
</style>
<details>
  <summary>Example</summary>
</details>
<details open>
  <summary>Example</summary>
</details>
