Every case below is pure HTML + CSS. Nothing here needs JavaScript; each one should work with scripting switched off.
The input generates no box at all, so only the label can be clicked. Expect the panel to appear and the button to turn red.
Clicking the words must toggle the checkbox next to them.
Regression guard: this always toggled, but the sibling rule used to be left selecting against the old state, so nothing appeared.
Turning one on must turn the other off, panels following.
Click a heading: it opens, the + becomes −, and the heading turns green. The second one starts open, so it should close.
Yes — the body is not boxed at all until open is set.
This one does, and clicking the heading must close it again.
The link must navigate; clicking anywhere else on the heading must toggle instead.
If you landed here the link won, which is correct.
Only the first summary discloses; the second is ordinary content and must stay hidden while closed.
body text