.nav { list-style: none; padding-left: 0; }
.nav-item { margin: 0.2em 0; }
.nested { display: none; list-style: none; padding-left: 1em; }
.nested.active { display: block; }
.toggle { cursor: pointer; user-select: none; }
.toggle::before { content: "▶ "; display: inline-block; transition: transform 0.2s; }
.toggle.expanded::before { transform: rotate(90deg); }