:root {
  --bg: #faf7f2;
  --surface: #ffffff;
  --surface-2: #f3eee6;
  --ink: #1c1917;
  --ink-2: #57534e;
  --ink-3: #8a837c;
  --line: #e7e0d5;
  --accent: #c2410c;
  --accent-soft: #fdebdd;
  --accent-ink: #ffffff;
  --good: #15803d;
  --good-soft: #dcfce7;
  --bad: #b91c1c;
  --bad-soft: #fee2e2;
  --warn: #a16207;
  --warn-soft: #fef3c7;
  --blue: #1d4ed8;
  --blue-soft: #dbeafe;
  --radius: 14px;
  --shadow: 0 1px 2px rgba(28, 25, 23, .05), 0 4px 16px rgba(28, 25, 23, .05);
  --serif: "Fraunces", Georgia, "Songti SC", serif;
  --sans: "Inter", -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", sans-serif;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #171412;
    --surface: #211d1a;
    --surface-2: #2a2521;
    --ink: #f5f0ea;
    --ink-2: #c4bcb2;
    --ink-3: #8f877e;
    --line: #37302a;
    --accent: #fb923c;
    --accent-soft: #3b2415;
    --accent-ink: #1c1917;
    --good: #4ade80;
    --good-soft: #14301f;
    --bad: #f87171;
    --bad-soft: #3a1818;
    --warn: #facc15;
    --warn-soft: #362d10;
    --blue: #93c5fd;
    --blue-soft: #172554;
    --shadow: none;
    color-scheme: dark;
  }
}

:root[data-theme="dark"] {
  --bg: #171412;
  --surface: #211d1a;
  --surface-2: #2a2521;
  --ink: #f5f0ea;
  --ink-2: #c4bcb2;
  --ink-3: #8f877e;
  --line: #37302a;
  --accent: #fb923c;
  --accent-soft: #3b2415;
  --accent-ink: #1c1917;
  --good: #4ade80;
  --good-soft: #14301f;
  --bad: #f87171;
  --bad-soft: #3a1818;
  --warn: #facc15;
  --warn-soft: #362d10;
  --blue: #93c5fd;
  --blue-soft: #172554;
  --shadow: none;
  color-scheme: dark;
}

* { box-sizing: border-box; }
[hidden] { display: none !important; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.6 var(--sans);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
a { color: var(--accent); }
h1, h2, h3 { font-family: var(--serif); font-weight: 700; line-height: 1.2; margin: 0 0 .5em; letter-spacing: -.01em; }
h1 { font-size: clamp(1.7rem, 4vw, 2.3rem); }
h2 { font-size: 1.35rem; }
h3 { font-size: 1.1rem; }
p { margin: 0 0 .9em; }
small, .muted { color: var(--ink-2); }
.faint { color: var(--ink-3); }
hr { border: 0; border-top: 1px solid var(--line); margin: 1.5rem 0; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 20;
  display: flex; align-items: center; gap: 1rem;
  padding: .6rem 1rem;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: .55rem; text-decoration: none; color: var(--ink); flex-shrink: 0; }
.brand-mark {
  display: grid; place-items: center; width: 34px; height: 34px; border-radius: 10px;
  background: var(--accent); color: var(--accent-ink); font: 700 .95rem var(--serif);
}
.brand-text { font: 700 1.05rem var(--serif); }
.nav { display: flex; gap: .25rem; overflow-x: auto; flex: 1; scrollbar-width: none; }
.nav::-webkit-scrollbar { display: none; }
.nav a {
  padding: .4rem .7rem; border-radius: 999px; text-decoration: none; color: var(--ink-2);
  font-size: .92rem; white-space: nowrap;
}
.nav a:hover { background: var(--surface-2); color: var(--ink); }
.nav a.active { background: var(--ink); color: var(--bg); }
.top-actions { display: flex; gap: .4rem; flex-shrink: 0; }

@media (max-width: 760px) {
  .topbar { flex-wrap: wrap; gap: .5rem; }
  .brand-text { display: none; }
  .nav { order: 3; flex-basis: 100%; }
  .top-actions { margin-left: auto; }
}

.container { width: 100%; max-width: 1080px; margin: 0 auto; padding: 1.5rem 16px 3rem; flex: 1; outline: none; }
.foot { text-align: center; padding: 1rem 16px 2rem; color: var(--ink-3); font-size: .85rem; }

/* ---------- building blocks ---------- */
.card {
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 1.1rem 1.2rem; box-shadow: var(--shadow);
}
.card + .card { margin-top: 1rem; }
.grid > .card + .card, .row > .card + .card { margin-top: 0; }
.grid { display: grid; gap: 1rem; }
.grid-2 { grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); }
.grid-3 { grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); }
.grid-4 { grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); }
.row { display: flex; gap: .6rem; align-items: center; flex-wrap: wrap; }
.row.between { justify-content: space-between; }
.stack > * + * { margin-top: .8rem; }
.spacer { flex: 1; }
.mt { margin-top: 1rem; }
.mt2 { margin-top: 2rem; }

.page-head { margin-bottom: 1.4rem; }
.page-head p { color: var(--ink-2); max-width: 64ch; }
.eyebrow { text-transform: uppercase; letter-spacing: .08em; font-size: .75rem; font-weight: 600; color: var(--accent); margin-bottom: .3rem; }

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: .4rem;
  padding: .55rem 1rem; border-radius: 10px; border: 1px solid var(--line);
  background: var(--surface); color: var(--ink); font: 500 .93rem var(--sans);
  cursor: pointer; text-decoration: none; min-height: 40px;
}
.btn:hover { border-color: var(--ink-3); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn.primary:hover { filter: brightness(1.06); }
.btn.ghost { background: transparent; }
.btn.danger { color: var(--bad); }
.btn.small { padding: .3rem .65rem; min-height: 32px; font-size: .85rem; }
.btn:disabled { opacity: .5; cursor: not-allowed; }
.chip {
  border: 1px solid var(--line); background: var(--surface); color: var(--ink-2);
  border-radius: 999px; padding: .3rem .7rem; font: 500 .85rem var(--sans); cursor: pointer; min-height: 32px;
}
.chip.on { background: var(--ink); color: var(--bg); border-color: var(--ink); }

.tag {
  display: inline-block; padding: .1rem .5rem; border-radius: 999px; font-size: .75rem; font-weight: 600;
  background: var(--surface-2); color: var(--ink-2);
}
.tag.accent { background: var(--accent-soft); color: var(--accent); }
.tag.good { background: var(--good-soft); color: var(--good); }
.tag.bad { background: var(--bad-soft); color: var(--bad); }
.tag.warn { background: var(--warn-soft); color: var(--warn); }
.tag.blue { background: var(--blue-soft); color: var(--blue); }

label { font-size: .9rem; color: var(--ink-2); display: block; margin-bottom: .25rem; }
input[type="text"], input[type="number"], input[type="date"], input[type="search"], select, textarea {
  width: 100%; padding: .55rem .7rem; border-radius: 10px; border: 1px solid var(--line);
  background: var(--surface); color: var(--ink); font: 16px/1.5 var(--sans);
}
input:focus, select:focus, textarea:focus { outline: 2px solid var(--accent); outline-offset: 1px; border-color: transparent; }
textarea { resize: vertical; }
.essay { min-height: 380px; font: 17px/1.75 Georgia, "Songti SC", serif; padding: 1rem; }

.tip {
  border-left: 3px solid var(--accent); background: var(--accent-soft);
  padding: .7rem .9rem; border-radius: 0 10px 10px 0; font-size: .93rem;
}
.tip.blue { border-color: var(--blue); background: var(--blue-soft); }
.zh { font-size: .9rem; color: var(--ink-2); }
.zh::before { content: "中 "; font-weight: 700; color: var(--accent); font-size: .75rem; }
body:not(.show-zh) .zh-only { display: none; }

/* ---------- stats ---------- */
.stat { display: flex; flex-direction: column; gap: .1rem; }
.stat .num { font: 700 2rem/1.1 var(--serif); }
.stat .lbl { font-size: .82rem; color: var(--ink-2); }
.big-band { font: 700 3.2rem/1 var(--serif); color: var(--accent); }

/* ---------- lists ---------- */
.list { list-style: none; margin: 0; padding: 0; }
.list li { padding: .7rem 0; border-bottom: 1px solid var(--line); }
.list li:last-child { border-bottom: 0; }
.item-link {
  display: block; text-decoration: none; color: inherit; padding: .9rem 1rem;
  border: 1px solid var(--line); border-radius: 12px; background: var(--surface);
}
.item-link:hover { border-color: var(--accent); }
.item-link h3 { margin: .2rem 0 .3rem; font-size: 1.02rem; }

.module-card { text-decoration: none; color: inherit; display: flex; flex-direction: column; gap: .3rem; }
.module-card:hover { border-color: var(--accent); }
.module-card .icon { font-size: 1.5rem; }

/* ---------- timer ---------- */
.timer {
  display: inline-flex; align-items: center; gap: .5rem;
  font: 600 1.25rem var(--sans); font-variant-numeric: tabular-nums;
  padding: .3rem .8rem; border-radius: 10px; background: var(--surface-2);
}
.timer.low { background: var(--bad-soft); color: var(--bad); }
.timer.done { background: var(--bad); color: #fff; }

/* ---------- writing ---------- */
.prompt-box { font: 1.05rem/1.65 Georgia, serif; }
.prompt-box .instr { font: .9rem var(--sans); color: var(--ink-2); margin-top: .6rem; }
.meter { display: flex; gap: 1rem; flex-wrap: wrap; font-size: .88rem; color: var(--ink-2); }
.meter b { color: var(--ink); font-variant-numeric: tabular-nums; }
.meter .ok b { color: var(--good); }
.meter .low b { color: var(--bad); }
.criteria { display: grid; gap: .8rem; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); }
.criteria .card { padding: .8rem 1rem; }
.checklist { list-style: none; padding: 0; margin: .4rem 0 0; font-size: .9rem; }
.checklist li { display: flex; gap: .5rem; align-items: flex-start; padding: .2rem 0; }
.checklist input { margin-top: .3rem; accent-color: var(--accent); }

/* ---------- chart ---------- */
.chart { width: 100%; max-width: 680px; height: auto; display: block; }
.chart text { fill: var(--ink-2); font: 12px var(--sans); }
.chart .axis { stroke: var(--line); }
.chart .grid-line { stroke: var(--line); stroke-dasharray: 3 3; }
table.data { border-collapse: collapse; width: 100%; font-size: .92rem; }
table.data th, table.data td { border: 1px solid var(--line); padding: .45rem .6rem; text-align: left; }
table.data th { background: var(--surface-2); font-weight: 600; }
table.data td.n { text-align: right; font-variant-numeric: tabular-nums; }
.table-wrap { overflow-x: auto; }
.process { display: flex; flex-wrap: wrap; gap: .5rem; align-items: center; counter-reset: step; }
.process .step {
  counter-increment: step; background: var(--surface-2); border-radius: 10px; padding: .5rem .7rem; font-size: .9rem;
}
.process .step::before { content: counter(step) ". "; font-weight: 700; color: var(--accent); }
.process .arrow { color: var(--ink-3); }

/* ---------- reading / listening ---------- */
.split { display: grid; grid-template-columns: 1.15fr 1fr; gap: 1rem; align-items: start; }
.split > .sticky { position: sticky; top: 76px; max-height: calc(100vh - 96px); overflow: auto; }
@media (max-width: 860px) {
  .split { grid-template-columns: 1fr; }
  .split > .sticky { position: static; max-height: none; }
}
.passage { font: 1rem/1.8 Georgia, "Songti SC", serif; }
.passage p { margin-bottom: 1em; }
.passage .para-label { font: 700 .85rem var(--sans); color: var(--accent); margin-right: .4rem; }
.q-group + .q-group { margin-top: 1.4rem; }
.q-group h3 { font: 600 .95rem var(--sans); }
.q-group .instr { font-size: .88rem; color: var(--ink-2); margin-bottom: .6rem; }
.q { padding: .6rem 0; border-bottom: 1px dashed var(--line); }
.q:last-child { border-bottom: 0; }
.q .qn { font-weight: 700; margin-right: .35rem; color: var(--accent); }
.q .opts { display: grid; gap: .25rem; margin-top: .35rem; }
.q .opts label { display: flex; gap: .45rem; align-items: flex-start; color: var(--ink); margin: 0; cursor: pointer; font-size: .95rem; }
.q .opts input { margin-top: .35rem; accent-color: var(--accent); }
.q select, .q input[type="text"] { max-width: 260px; margin-top: .3rem; }
.q.right { background: var(--good-soft); border-radius: 8px; padding-left: .5rem; padding-right: .5rem; }
.q.wrong { background: var(--bad-soft); border-radius: 8px; padding-left: .5rem; padding-right: .5rem; }
.q .explain { margin-top: .45rem; font-size: .9rem; color: var(--ink-2); }
.q .explain b { color: var(--ink); }
.inline-gap { display: inline-block; width: 150px; margin: 0 .2rem; }
.form-sheet { background: var(--surface-2); border-radius: 12px; padding: 1rem; }
.form-sheet .q { border-bottom-color: var(--line); }
.transcript .line { padding: .35rem 0; }
.transcript .who { font-weight: 700; color: var(--accent); margin-right: .4rem; font-size: .88rem; }
mark { background: var(--warn-soft); color: inherit; padding: 0 .15em; border-radius: 3px; }

.player { display: flex; align-items: center; gap: .6rem; flex-wrap: wrap; }
.player .bar { flex: 1; min-width: 160px; height: 6px; background: var(--surface-2); border-radius: 999px; overflow: hidden; }
.player .bar i { display: block; height: 100%; background: var(--accent); width: 0; transition: width .3s; }

/* ---------- speaking ---------- */
.cue-card {
  border: 2px solid var(--ink); border-radius: 14px; padding: 1.2rem 1.4rem; background: var(--surface);
  font: 1.05rem/1.6 Georgia, serif;
}
.cue-card h2 { font-size: 1.25rem; }
.cue-card ul { margin: .3rem 0 .6rem 1.1rem; padding: 0; }
.rec-dot { width: 10px; height: 10px; border-radius: 50%; background: var(--bad); display: inline-block; animation: pulse 1s infinite; }
@keyframes pulse { 50% { opacity: .25; } }
audio { width: 100%; max-width: 420px; }

/* ---------- vocab ---------- */
.flash {
  min-height: 260px; display: flex; flex-direction: column; align-items: center; justify-content: center;
  text-align: center; gap: .5rem; padding: 2rem 1.2rem;
}
.flash .word { font: 700 2.4rem/1.1 var(--serif); }
.flash .pos { color: var(--ink-3); font-style: italic; }
.flash .meaning { font-size: 1.1rem; max-width: 46ch; }
.flash .cn { font-size: 1.15rem; color: var(--accent); }
.flash .ex { font-style: italic; color: var(--ink-2); max-width: 52ch; }
.boxes { display: flex; gap: .4rem; }
.boxes span { flex: 1; text-align: center; padding: .4rem 0; border-radius: 8px; background: var(--surface-2); font-size: .8rem; }
.boxes b { display: block; font: 700 1.2rem var(--serif); }

/* ---------- heatmap ---------- */
.heat { display: grid; grid-template-rows: repeat(7, 13px); grid-auto-flow: column; grid-auto-columns: 13px; gap: 3px; }
.heat i { border-radius: 3px; background: var(--surface-2); }
.heat i.l1 { background: color-mix(in srgb, var(--accent) 30%, var(--surface-2)); }
.heat i.l2 { background: color-mix(in srgb, var(--accent) 60%, var(--surface-2)); }
.heat i.l3 { background: var(--accent); }

.toast {
  position: fixed; left: 50%; bottom: 24px; transform: translateX(-50%);
  background: var(--ink); color: var(--bg); padding: .6rem 1rem; border-radius: 10px;
  font-size: .92rem; z-index: 50; box-shadow: var(--shadow); max-width: calc(100vw - 32px);
}
.empty { text-align: center; padding: 2rem 1rem; color: var(--ink-3); }
.kbd { font: 600 .8rem ui-monospace, monospace; padding: .05rem .35rem; border: 1px solid var(--line); border-radius: 5px; background: var(--surface-2); }