ul.collapsible{list-style:none;margin:0 0 12px;padding:0;border:1px solid #e5e7eb;border-radius:8px;overflow:hidden}
  ul.collapsible>h3{margin:0;padding:12px 14px;cursor:pointer;user-select:none;background:#f9fafb;font-size:16px;display:flex;justify-content:space-between;align-items:center}
  /* 指示箭頭 */
  ul.collapsible>h3::after{content:"▾";transition:transform .2s}
  ul.collapsible.is-collapsed>h3::after{transform:rotate(-90deg)}
  /* 收合時隱藏 li */
  ul.collapsible.is-collapsed>li{display:none}
  /* 項目樣式 */
  ul.collapsible>li{padding:8px 14px;border-top:1px solid #eee}
  ul.collapsible>li a{text-decoration:none}
  ul.collapsible>li a:hover{text-decoration:underline}