:root {
  --bg: #f6f6f3; --card: #ffffff; --ink: #1c1c1e; --mute: #6b6b70; --line: #e4e4e0;
  --accent: #2f6fed; --accent-ink: #ffffff; --soft: #eef3ff;
  --ok: #1d7a46; --ok-soft: #e7f5ec; --warn: #a8530d; --warn-soft: #fdf1e5; --bad: #b42318;
  --rec: #d92d20;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #141416; --card: #1e1e21; --ink: #ececee; --mute: #9a9aa1; --line: #323237;
    --accent: #6d9bff; --accent-ink: #0b1020; --soft: #1d2740;
    --ok: #5fcf8d; --ok-soft: #16301f; --warn: #f0a35e; --warn-soft: #33240f; --bad: #ff8a80; --rec: #ff6b5f;
  }
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 16px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; }
a { color: var(--accent); text-decoration: none; }
.top { position: sticky; top: 0; z-index: 5; display: flex; align-items: center; justify-content: space-between; gap: 12px;
  padding: 10px 16px; padding-top: max(10px, env(safe-area-inset-top)); background: var(--card); border-bottom: 1px solid var(--line); }
.brand { font-weight: 700; color: var(--ink); }
.top { justify-content: flex-start; }
.menu-btn { border: 0; background: none; font-size: 1.3rem; padding: 2px 6px; line-height: 1; }
main { max-width: 680px; margin: 0 auto; padding: 16px; }

/* ---------- 目录：手机是抽屉，电脑常驻左边 ---------- */
.sidebar { position: fixed; z-index: 20; top: 0; bottom: 0; left: 0; width: min(86vw, 320px); overflow-y: auto;
  background: var(--card); border-right: 1px solid var(--line); padding: 12px 10px 40px; padding-top: max(12px, env(safe-area-inset-top));
  transform: translateX(-102%); transition: transform .2s ease; }
.sidebar.open { transform: none; box-shadow: 0 0 40px rgba(0,0,0,.25); }
.backdrop { position: fixed; inset: 0; z-index: 15; background: rgba(0,0,0,.35); }
@media (min-width: 960px) {
  .menu-btn, .backdrop { display: none !important; }
  .layout { display: grid; grid-template-columns: 300px minmax(0, 1fr); }
  .sidebar { position: sticky; top: 49px; height: calc(100vh - 49px); width: auto; transform: none; box-shadow: none; z-index: 1; }
}
#nav a, #nav summary { display: flex; justify-content: space-between; align-items: center; gap: 8px; padding: 8px 10px; border-radius: 10px; color: var(--ink); cursor: pointer; }
#nav a:hover, #nav summary:hover { background: var(--bg); }
#nav a.current { background: var(--soft); color: var(--accent); font-weight: 600; }
#nav summary { list-style: none; font-weight: 600; }
#nav summary::-webkit-details-marker { display: none; }
#nav summary::before { content: '▸'; color: var(--mute); margin-right: 2px; transition: transform .15s; }
#nav details[open] > summary::before { transform: rotate(90deg); }
#nav summary > :first-child { flex: 1; }
#nav details details { margin-left: 12px; }
#nav details details summary { font-weight: 500; }
#nav details details a { margin-left: 14px; font-size: .93rem; }
#nav .n { color: var(--mute); font-size: .82rem; font-weight: 400; flex: none; }
#nav .sep { border-top: 1px solid var(--line); margin: 8px 4px; }
#nav .hw { background: var(--soft); border-radius: 12px; padding: 8px 6px; margin: 6px 0 4px; }
#nav .hw .hw-title { padding: 2px 10px; font-weight: 700; }
#nav .hw .hw-meta { padding: 0 10px 4px; color: var(--mute); font-size: .82rem; }
#nav .hw .progress { margin: 4px 10px 6px; }
.seg { display: inline-flex; border: 1px solid var(--line); border-radius: 10px; overflow: hidden; }
.seg button { border: 0; border-radius: 0; padding: 6px 14px; }
.seg button.on { background: var(--accent); color: var(--accent-ink); }
.parts { width: 100%; border-collapse: collapse; font-size: .92rem; }
.parts td, .parts th { text-align: left; padding: 8px 4px; border-top: 1px solid var(--line); }
.parts th { color: var(--mute); font-weight: 500; border-top: 0; }
.bad { color: var(--warn); font-weight: 600; }
.okc { color: var(--ok); font-weight: 600; }
details.q { border-top: 1px solid var(--line); }
details.q > summary { cursor: pointer; padding: 10px 0; list-style: none; display: flex; justify-content: space-between; gap: 8px; }
details.q > summary::-webkit-details-marker { display: none; }
.attempt { border-left: 3px solid var(--line); padding: 4px 0 8px 12px; margin: 8px 0; }
.foot { max-width: 680px; margin: 0 auto; padding: 8px 16px 32px; color: var(--mute); font-size: .8rem; }
h1 { font-size: 1.35rem; margin: 4px 0 12px; }
h2 { font-size: 1.05rem; margin: 0 0 8px; }
.card { background: var(--card); border: 1px solid var(--line); border-radius: 14px; padding: 16px; margin-bottom: 14px; }
.mute { color: var(--mute); }
.small { font-size: .88rem; }
.row { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }
.spread { display: flex; justify-content: space-between; align-items: center; gap: 8px; }
button, .btn, select, input { font: inherit; }
button, .btn { border-radius: 12px; border: 1px solid var(--line); background: var(--card); color: var(--ink); padding: 10px 16px; cursor: pointer; display: inline-block; text-align: center; }
button.primary, .btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); font-weight: 600; }
button.rec { background: var(--rec); border-color: var(--rec); color: #fff; font-weight: 700; }
button.big { width: 100%; padding: 16px; font-size: 1.1rem; }
button:disabled { opacity: .5; cursor: default; }
button.link { border: 0; background: none; color: var(--accent); padding: 4px 0; }
select, input[type=text] { width: 100%; min-width: 0; padding: 10px 12px; border-radius: 10px; border: 1px solid var(--line); background: var(--card); color: var(--ink); }
.chips { display: flex; flex-wrap: wrap; gap: 6px; }
.chip { font-size: .85rem; padding: 3px 10px; border-radius: 999px; background: var(--soft); color: var(--ink); }
.chip.ok { background: var(--ok-soft); color: var(--ok); }
.chip.new { background: var(--warn-soft); color: var(--warn); }
.tag { font-size: .75rem; font-weight: 600; text-transform: uppercase; letter-spacing: .03em; color: var(--mute); }
.progress { height: 8px; border-radius: 6px; background: var(--line); overflow: hidden; margin: 8px 0; }
.progress i { display: block; height: 100%; background: var(--ok); }
.list { list-style: none; margin: 0; padding: 0; }
.list li { border-top: 1px solid var(--line); }
.list li:first-child { border-top: 0; }
.list a, .list .item { display: flex; gap: 10px; align-items: flex-start; justify-content: space-between; padding: 10px 0; color: var(--ink); }
.done-mark { color: var(--ok); font-weight: 700; flex: none; }
.todo-mark { color: var(--line); flex: none; }
.question { font-size: 1.25rem; font-weight: 650; line-height: 1.35; margin: 4px 0 8px; }
.cue { margin: 8px 0 0 20px; padding: 0; }
.clock { font-size: 2.4rem; font-weight: 750; font-variant-numeric: tabular-nums; }
.meter { height: 10px; background: var(--line); border-radius: 6px; overflow: hidden; margin: 8px 0 14px; }
.meter i { display: block; height: 100%; width: 0; background: var(--accent); transition: width .05s linear; }
.stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(120px, 1fr)); gap: 10px; margin-bottom: 10px; }
.stat b { display: block; font-size: 1.25rem; }
.stat span { color: var(--mute); font-size: .82rem; }
.hint { background: var(--warn-soft); color: var(--warn); border-radius: 10px; padding: 8px 12px; margin: 6px 0; }
.good { background: var(--ok-soft); color: var(--ok); border-radius: 10px; padding: 8px 12px; margin: 6px 0; }
.transcript { white-space: pre-wrap; background: var(--bg); border-radius: 10px; padding: 10px 12px; }
.err { margin: 6px 0; }
.err s { color: var(--bad); }
.err b { color: var(--ok); }
audio { width: 100%; margin: 8px 0; }
.filters { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 8px; margin-bottom: 12px; }
.tip { border-left: 4px solid var(--accent); padding: 4px 0 4px 12px; margin: 8px 0; }
.toast { position: fixed; left: 50%; bottom: 24px; transform: translateX(-50%); background: var(--ink); color: var(--bg); padding: 10px 16px; border-radius: 10px; z-index: 10; max-width: calc(100% - 32px); }
.example { background: var(--soft); border-radius: 12px; padding: 12px 14px; margin: 14px 0 4px; }
.example p { margin: 6px 0 0; }