Indice

Main chapter

This is the information in the chapter.

It can also include lists of elements:

This is an element in a list.

This is another element in the list.

You can click on the arrow to collapse the whole chapter (but not any subchapters it may contain).

Subchapter

This is the information in the sub chapter.

It can also include lists of elements:

This is an element in a list.

This is another element in the list.

You can click on the arrow to collapse the subchapter.

Code:

<details open="">
<summary style="font-weight:bold;font-size:1.25em;line-height:1.3;margin:0">
Main chapter
</summary>
<p>This is the information in the chapter.</p>
</details>