This panel contains the detailed information for the widget. It's controlled by the button above using aria-expanded and aria-controls. The container uses the class "details" as requested.
The open/close transition is animated (unless the user prefers reduced motion). When expanded, the button's aria-expanded becomes "true" and the details are exposed to assistive technologies.
You can put any content here — text, images, or links. Example link:
Accessible Accordion Guidance.