Dropdown Spacing and Classes
:margin: takes either one value, applying to every side, or exactly four,
read as top bottom left right — note the order, which is neither CSS's
clockwise one nor alphabetical. Each value is auto or a step from 0 to
5. Writing no :margin: is not the same as writing 0: the default
keeps a bottom margin so consecutive dropdowns do not touch.
One value, every side
:margin: 4
Four values, top bottom left right
:margin: 0 4 auto auto — no space above, a wide gap below, and centred
horizontally.
The three class options are the escape hatch for anything the vocabulary above
does not cover. Each lands on its own element: the <details>, the
<summary>, and the content <div>.
Carrying custom classes
The stylesheet this site ships defines none of these three, so they change nothing here — they are what a project's own CSS would hook into.