/* <dfn data-def="説明">用語</dfn> でツールチップ */
dfn{font-style:normal;border-bottom:1px dotted var(--line);cursor:help;position:relative}
dfn:focus, dfn:hover{outline:none}
dfn[data-def]::after{
  content: attr(data-def);
  position:absolute; left:0; top:1.6em; z-index:30; min-width:200px; max-width:320px;
  background:#fff; color:var(--ink); border:1px solid var(--line); border-radius:10px;
  padding:8px 10px; box-shadow:0 8px 24px rgba(0,0,0,.08); font-size:.9rem; line-height:1.5;
  opacity:0; transform:translateY(-4px); pointer-events:none; transition:.12s ease;
}
dfn:hover::after, dfn:focus::after{opacity:1; transform:translateY(0)}