Spoiler. Ability to control visibility of the content in posts. Works better with Markdown syntax.
Example:
:::
Spoiler's content goes here, it should start and end with at least 3 colons.
It should have a blank lines around the 3 colons tags.
:::
Markdown syntax is based on ideas from CommonMark Talk group.
This is true spoiler implementation where spoiler content is not loaded on the page (loading on demand or "lazy loading").
If you want to alter look of the spoiler, you could use these CSS classes:
ns-spoilerns-spoiler-controlns-spoiler-content