:root {
  /* 只做浅色：不要暗色背景（AGENTS.md 铁律，test/light-theme.test.mjs 机检） */
  color-scheme: light;
  --bg: #f6f8fb;
  --surface: #ffffff;
  --surface-2: #eef2f7;
  --text: #1e293b;
  --muted: #5b6b7f;
  --accent: #0f766e;
  --accent-2: #4f46e5;
  --on-accent: #ffffff;
  --accent-soft: rgba(15, 118, 110, 0.1);
  --accent-line: rgba(15, 118, 110, 0.28);
  --border: rgba(15, 23, 42, 0.1);
  --shadow: 0 10px 30px rgba(15, 23, 42, 0.08);
  --radius: 16px;
  --sticky-offset: calc(4.65rem + env(safe-area-inset-top, 0px));
  /* 动效令牌：与 src/motion-math.mjs 的 MOTION / EASING 同一张表（test/style-tokens.test.mjs 对账） */
  --dur-instant: 90ms;
  --dur-fast: 160ms;
  --dur-base: 240ms;
  --dur-slow: 360ms;
  --dur-deliberate: 560ms;
  --ease-standard: cubic-bezier(0.2, 0, 0, 1);
  --ease-decelerate: cubic-bezier(0.05, 0.7, 0.1, 1);
  --ease-accelerate: cubic-bezier(0.3, 0, 0.8, 0.15);
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
  --stagger-step: 45ms;
  font-family: "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
}

* { box-sizing: border-box; }
html, body { margin: 0; min-height: 100%; background: var(--bg); color: var(--text); }
body {
  background:
    radial-gradient(ellipse 80% 50% at 50% -20%, rgba(15, 118, 110, 0.12), transparent),
    radial-gradient(ellipse 60% 40% at 100% 0%, rgba(99, 102, 241, 0.1), transparent),
    var(--bg);
}

.skip-link {
  position: absolute; left: -9999px;
}
.skip-link:focus { left: 1rem; top: 1rem; z-index: 9; background: var(--accent); color: var(--on-accent); padding: 0.5rem 1rem; border-radius: 8px; }

.topbar {
  display: flex; align-items: center; justify-content: space-between; gap: 0.75rem;
  padding-top: max(0.85rem, env(safe-area-inset-top));
  padding-bottom: 0.85rem;
  padding-left: max(1.25rem, env(safe-area-inset-left));
  padding-right: max(1.25rem, env(safe-area-inset-right));
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(12px); position: sticky; top: 0; z-index: 5;
  background: rgba(255, 255, 255, 0.9);
}
.brand { display: flex; gap: 0.85rem; align-items: center; }
.brand-mark {
  width: 42px; height: 42px; border-radius: 12px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  box-shadow: 0 0 24px rgba(15, 118, 110, 0.35);
}
.topbar h1 { margin: 0; font-size: 1.1rem; letter-spacing: 0.02em; }
.tagline { margin: 0.15rem 0 0; font-size: 0.78rem; color: var(--muted); }
.pill {
  font-size: 0.78rem; padding: 0.35rem 0.75rem; border-radius: 999px;
  background: var(--surface-2); border: 1px solid var(--border);
}

main { max-width: 920px; padding-bottom: max(1.25rem, env(safe-area-inset-bottom)); margin: 0 auto; padding: 1.25rem; }
.view { display: none; }
.view.active { display: block; }

.hero { margin-bottom: 1.5rem; }
.eyebrow { color: var(--accent); font-size: 0.82rem; letter-spacing: 0.08em; text-transform: uppercase; }
.hero h2 { font-size: clamp(1.5rem, 4vw, 2rem); margin: 0.35rem 0; line-height: 1.25; }
.lead { color: var(--muted); line-height: 1.6; max-width: 52ch; }

.section-title { font-size: 1rem; margin: 0 0 0.75rem; color: var(--muted); }

.grid-subjects {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 0.85rem;
}

.course-card {
  position: relative;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 1.25rem; box-shadow: var(--shadow); cursor: pointer;
  transition: transform var(--dur-base) var(--ease-decelerate), border-color var(--dur-base);
}
.course-card:hover { transform: translateY(-3px); border-color: rgba(15, 118, 110, 0.35); }
.course-card h3 { margin: 0 0 0.35rem; }
.course-meta { display: flex; gap: 0.75rem; flex-wrap: wrap; font-size: 0.82rem; color: var(--muted); margin-bottom: 0.75rem; }
.progress-bar {
  height: 6px; border-radius: 999px; background: var(--surface-2); overflow: hidden;
}
.progress-bar > span {
  display: block; height: 100%; background: linear-gradient(90deg, var(--accent), var(--accent-2));
  transition: width var(--dur-slow) var(--ease-decelerate);
}
.lesson-chips { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-top: 0.85rem; }
.chip {
  cursor: pointer;
  font-size: 0.72rem; padding: 0.2rem 0.55rem; border-radius: 999px;
  background: var(--surface-2); border: 1px solid var(--border);
}
.chip.done { border-color: rgba(15, 118, 110, 0.5); color: var(--accent); }
.subject-badge {
  position: absolute; top: 1rem; right: 1rem; width: 32px; height: 32px; border-radius: 8px;
  display: grid; place-items: center; font-weight: 700; font-size: 0.9rem;
  background: var(--surface-2); border: 1px solid var(--border);
}

.lesson-nav { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 1rem; }
.review-status { font-size: 0.85rem; color: var(--accent-2); margin-top: 0.5rem; }
.phase-block h3 { font-size: 0.9rem; color: var(--muted); margin: 0 0 0.5rem; }
.phase-columns { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; margin: 1rem 0; }
.lesson-steps.interact li { color: var(--text); transition: color var(--dur-fast), opacity var(--dur-fast), background var(--dur-fast); }
.lesson-steps.interact li.done { color: var(--accent); opacity: 1; }
.lesson-steps.interact li.done::before { content: '✓ '; color: var(--accent); }
@media (max-width: 700px) {
  .phase-columns { grid-template-columns: 1fr; gap: 0.85rem; }
}
.crumb { color: var(--muted); font-size: 0.85rem; }
.lesson-shell {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 1.25rem; box-shadow: var(--shadow);
}
.lesson-header h2 { margin: 0 0 0.35rem; }
.muted { color: var(--muted); line-height: 1.55; }

.demo-stage {
  margin: 1.25rem 0; min-height: 220px; border-radius: 14px;
  background:
    radial-gradient(ellipse 80% 50% at 50% 0%, rgba(15, 118, 110, 0.07), transparent 60%),
    linear-gradient(180deg, var(--surface-2), var(--bg));
  border: 1px solid var(--border);
  display: grid; place-items: center; position: relative; overflow: hidden;
  padding: 1rem;
  width: 100%;
  max-width: 100%;
  color: var(--text);
  box-shadow: inset 0 1px 0 rgba(15, 23, 42, 0.03);
}
.demo-stage > * { max-width: 100%; }
.demo-controls {
  display: flex; flex-wrap: wrap; gap: 0.75rem; align-items: center; margin-bottom: 1rem;
}
.demo-controls label,
.demo-slider {
  font-size: 0.85rem; color: var(--muted); display: flex; gap: 0.5rem; align-items: center; min-width: 0;
}
.demo-controls input[type="range"],
.demo-slider input[type="range"] {
  width: min(180px, 46vw); accent-color: var(--accent); min-width: 0;
}

.lesson-steps { padding-left: 1.2rem; line-height: 1.65; color: var(--text); }
.lesson-steps li { margin-bottom: 0.5rem; transition: color var(--dur-fast), opacity var(--dur-fast), background var(--dur-fast), border-color var(--dur-fast); }
.lesson-steps.explain-sync {
  list-style: none;
  padding-left: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}
.lesson-steps.explain-sync li {
  opacity: 0.62;
  color: var(--muted);
  padding: 0.5rem 0.7rem;
  border-radius: 10px;
  border: 1px solid transparent;
  border-left: 3px solid transparent;
  background: rgba(15, 23, 42, 0.03);
  overflow-wrap: anywhere;
}
.lesson-steps.explain-sync li.seen {
  opacity: 0.9;
  color: var(--text);
}
.lesson-steps.explain-sync li.active {
  opacity: 1;
  color: var(--text);
  font-weight: 600;
  border-color: var(--accent-line);
  border-left-color: var(--accent);
  background: var(--accent-soft);
  box-shadow: inset 0 0 0 1px rgba(15, 118, 110, 0.08);
  scroll-margin-top: calc(var(--sticky-offset) + 3.5rem);
}
.lesson-steps.explain-sync li.active .step-tag {
  background: var(--accent);
  color: var(--on-accent);
}
.explain-live {
  margin: 0.75rem 0 0;
  padding: 0.75rem 0.9rem 0.8rem 1rem;
  border-radius: 12px;
  border: 1px solid var(--accent-line);
  border-left: 3px solid var(--accent);
  background: linear-gradient(90deg, rgba(15, 118, 110, 0.12), rgba(79, 70, 229, 0.05));
  font-size: 0.9rem;
  line-height: 1.55;
  color: var(--text);
  min-height: 2.8em;
  overflow-wrap: anywhere;
}
.explain-live::before {
  content: '当前讲解';
  display: block;
  font-size: 0.68rem;
  letter-spacing: 0.12em;
  color: var(--accent);
  margin-bottom: 0.28rem;
  font-weight: 650;
}
.lesson-phase-nav {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.4rem;
  margin: 0 0 1rem;
}
.lesson-phase-nav .phase-chip {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  font-size: clamp(0.68rem, 2.6vw, 0.78rem);
  padding: 0.4rem 0.35rem;
  border-radius: 999px;
  border: 1px solid var(--border);
  color: var(--muted);
  background: var(--surface-2);
  text-align: center;
  line-height: 1.25;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.lesson-phase-nav .phase-chip.active {
  border-color: rgba(15, 118, 110, 0.5);
  color: var(--accent);
  background: var(--accent-soft);
  font-weight: 650;
  box-shadow: 0 0 0 1px rgba(15, 118, 110, 0.12);
}
.lesson-phase-nav .phase-chip.done {
  border-color: rgba(15, 118, 110, 0.28);
  color: var(--accent);
  background: rgba(15, 118, 110, 0.05);
}
.quiz-gate {
  margin: 1rem 0 0.5rem;
  padding: 0.9rem 1rem;
  border-radius: 12px;
  border: 1px solid rgba(79, 70, 229, 0.28);
  border-left: 3px solid var(--accent-2);
  background: linear-gradient(180deg, rgba(79, 70, 229, 0.08), var(--surface-2));
  font-size: 0.88rem;
  color: var(--muted);
  line-height: 1.55;
}
.quiz-gate p { margin: 0; color: var(--muted); }

.quiz-panel {
  margin: 1rem 0; padding: 1rem; border-radius: 12px;
  background: var(--surface-2); border: 1px solid var(--border);
}
.quiz-panel fieldset { border: 0; margin: 0; padding: 0; }
.quiz-panel legend { font-weight: 600; margin-bottom: 0.65rem; }
.quiz-choice {
  display: block; margin: 0.35rem 0; padding: 0.7rem 0.85rem; border-radius: 10px;
  background: rgba(15, 23, 42, 0.03); border: 1px solid transparent; cursor: pointer;
  min-height: 44px; color: var(--text); touch-action: manipulation;
}
.quiz-choice:hover { border-color: var(--border); }
.quiz-feedback { margin-top: 0.65rem; font-size: 0.9rem; }
.quiz-feedback.ok { color: var(--accent); }
.quiz-feedback.bad { color: #dc2626; }

.lesson-footer { display: flex; gap: 0.65rem; flex-wrap: wrap; margin-top: 1.25rem; }

.btn {
  min-height: 44px;
  touch-action: manipulation;
  border: 0; border-radius: 10px; padding: 0.6rem 1rem; font-size: 0.92rem; cursor: pointer;
  transition: transform var(--dur-fast) var(--ease-decelerate), box-shadow var(--dur-fast);
}
.btn.primary { background: linear-gradient(135deg, var(--accent), #115e59); color: var(--on-accent); font-weight: 600; }
.btn.ghost { background: transparent; color: var(--text); border: 1px solid var(--border); }
.btn:hover { transform: translateY(-1px); }
.btn:disabled { opacity: 0.45; cursor: not-allowed; transform: none; }

/* 学科演示 */
.demo-graph { width: 100%; text-align: center; }
.graph-svg { width: min(320px, 100%); height: auto; }
.graph-svg .curve { fill: none; stroke-width: 3; }
.demo-caption { font-size: 0.85rem; color: var(--muted); margin-top: 0.5rem; }

.clause-demo { display: flex; gap: 0.5rem; flex-wrap: wrap; justify-content: center; }
.clause-demo span {
  padding: 0.5rem 0.75rem; border-radius: 10px; border: 1px solid var(--border);
  opacity: 0.35;
}
.clause-demo span[data-r="主"] { border-color: #0f766e; }
.clause-demo span[data-r="谓"] { border-color: #4f46e5; }
.clause-demo span[data-r="宾"] { border-color: #b45309; }

.english-demo .line { font-size: 1.1rem; padding: 0.35rem; }
.english-demo .ques { color: var(--accent); opacity: 0; }

.projectile-demo { width: 100%; height: 160px; position: relative; }
.projectile-demo .ball {
  width: 16px; height: 16px; border-radius: 50%; background: var(--accent);
  position: absolute; left: 10%; top: 15%;
}

.bond-demo { display: flex; align-items: center; gap: 0; position: relative; min-height: 100px; }
.bond-demo .atom { width: 48px; height: 48px; border-radius: 50%; background: radial-gradient(circle, #4f46e5, #4338ca); }
.bond-demo .overlap {
  position: absolute; width: 40px; height: 40px; border-radius: 50%;
  background: rgba(15, 118, 110, 0.35); left: 50%; transform: translateX(-50%);
}

.cell-demo {
  width: 140px; height: 140px; border-radius: 50%; border: 2px solid var(--accent);
  position: relative; display: grid; place-items: center;
}
.cell-demo .layer {
  position: absolute; border-radius: 50%; display: grid; place-items: center; font-size: 0.7rem;
}
.cell-demo .layer:nth-child(1) { inset: 0; border: 2px solid #0f766e; }
.cell-demo .layer:nth-child(2) { inset: 12px; border: 1px dashed #64748b; }
.cell-demo .layer:nth-child(3) { inset: 36px; background: #6366f1; width: 40px; height: 40px; }
.cell-demo .layer:nth-child(4) { bottom: 28px; right: 18px; width: 20px; height: 20px; background: #f97316; font-size: 0.55rem; }

.timeline-demo { width: 100%; max-width: 100%; overflow-x: auto; -webkit-overflow-scrolling: touch; }
.timeline-demo .track {
  display: flex; gap: 1.5rem; align-items: center; border-bottom: 2px solid var(--border);
  padding-bottom: 0.5rem; min-width: 280px;
}
.timeline-demo .event {
  opacity: 0; padding: 0.35rem 0.6rem; border-radius: 8px; background: var(--surface-2);
  border: 1px solid var(--border); font-size: 0.85rem;
}

.earth-demo { position: relative; width: 200px; height: 100px; }
.earth-demo .sun {
  position: absolute; right: 0; top: 20px; width: 32px; height: 32px; border-radius: 50%;
  background: #b45309; box-shadow: 0 0 20px #b45309;
}
.earth-demo .earth {
  position: absolute; left: 40px; top: 30px; width: 48px; height: 48px; border-radius: 50%;
  background: linear-gradient(135deg, #3b82f6, #166534);
  transform-origin: 100px 44px;
}

.balance-demo { text-align: center; }
.balance-demo .beam {
  display: flex; justify-content: space-between; width: 200px;
  border-bottom: 4px solid #64748b; transform-origin: center bottom;
}
.balance-demo .fulcrum {
  width: 0; height: 0; border-left: 12px solid transparent; border-right: 12px solid transparent;
  border-bottom: 20px solid #64748b; margin: 0 auto;
}
.balance-demo .left-pan, .balance-demo .right-pan { font-size: 0.8rem; padding: 0.25rem; }

.card-seq { display: flex; flex-direction: column; gap: 0.45rem; width: 100%; max-width: 320px; margin: 0 auto; }
.seq-card {
  padding: 0.55rem 0.75rem; border-radius: 10px; background: var(--surface-2);
  border: 1px solid var(--border); opacity: 0; font-size: 0.9rem;
}

.unit-circle { width: min(220px, 100%); height: auto; }
.unit-circle .ray { transform-origin: 100px 100px; }

.pyth-demo {
  position: relative; width: 180px; height: 140px; margin: 0 auto;
}
.pyth-demo .sq {
  position: absolute; display: grid; place-items: center; font-size: 0.75rem;
  border: 1px solid var(--border); border-radius: 6px; background: rgba(15, 23, 42, 0.03);
}
.pyth-demo .sq.a { width: 60px; height: 60px; left: 0; bottom: 0; }
.pyth-demo .sq.b { width: 80px; height: 80px; left: 62px; bottom: 0; }
.pyth-demo .sq.c { width: 100px; height: 100px; right: 0; top: 0; border-color: var(--accent); }
.pyth-demo .tri {
  position: absolute; left: 0; bottom: 0; width: 0; height: 0;
  border-left: 60px solid transparent; border-bottom: 80px solid rgba(15, 118, 110,0.25);
}

.dual-line { display: flex; flex-direction: column; gap: 0.65rem; text-align: center; }
.dual-line .metaphor { color: var(--muted); }
.dual-line .person { color: var(--accent); font-weight: 600; }

.word-morph { display: flex; flex-wrap: wrap; gap: 0.5rem; justify-content: center; }
.word-morph span {
  padding: 0.45rem 0.65rem; border-radius: 8px; background: var(--surface-2);
  border: 1px solid var(--border); font-size: 0.9rem;
}

.highlight-sentence { font-size: 1.05rem; line-height: 1.6; text-align: center; }
.highlight-sentence mark { background: rgba(15, 118, 110,0.25); color: var(--accent); padding: 0 0.2rem; border-radius: 4px; }

.inertia-demo { position: relative; width: 100%; height: 100px; }
.inertia-demo .cart {
  position: absolute; left: 10%; bottom: 20px; width: 80px; height: 36px;
  background: #64748b; border-radius: 6px;
}
.inertia-demo .block {
  position: absolute; left: 18%; bottom: 56px; width: 24px; height: 24px;
  background: var(--accent); border-radius: 4px;
}

.ionic-demo { display: flex; align-items: center; gap: 0.75rem; justify-content: center; font-size: 1.2rem; font-weight: 600; }
.ionic-demo .na { color: #4f46e5; }
.ionic-demo .cl { color: #059669; }
.ionic-demo .e { color: var(--muted); font-size: 0.85rem; }

.eq-demo span {
  font-family: ui-monospace, Consolas, monospace; font-size: 1.05rem;
  padding: 0.65rem 1rem; border-radius: 10px; background: var(--surface-2);
  border: 1px solid var(--border);
}

.periodic-row { display: flex; gap: 0.35rem; justify-content: center; flex-wrap: wrap; }
.periodic-row span {
  width: 36px; height: 36px; display: grid; place-items: center; border-radius: 8px;
  background: var(--surface-2); border: 1px solid var(--border); font-size: 0.8rem;
}

.dna-demo { display: flex; gap: 8px; justify-content: center; min-height: 100px; }
.dna-demo .strand {
  width: 12px; height: 80px; border-radius: 6px;
  background: linear-gradient(180deg, #4f46e5, #0f766e);
}

.contour-svg { width: min(280px, 100%); height: auto; }

.front-demo { display: flex; flex-direction: column; gap: 0.5rem; text-align: center; }
.front-demo .cold { color: #2563eb; }
.front-demo .warm { color: #dc2626; }

.pyramid { display: flex; flex-direction: column; gap: 0.35rem; max-width: 240px; margin: 0 auto; }
.pyramid .bar { height: 18px; border-radius: 6px; background: linear-gradient(90deg, var(--accent), var(--accent-2)); }

.factory-demo { display: flex; gap: 1rem; justify-content: center; align-items: center; font-size: 1.1rem; }
.factory-demo .factory { padding: 0.5rem 0.75rem; border-radius: 8px; background: var(--surface-2); border: 1px solid var(--border); }
.factory-demo .res, .factory-demo .mkt { color: var(--muted); font-size: 0.9rem; }

.boundary-demo { display: flex; gap: 0.75rem; justify-content: center; flex-wrap: wrap; }
.boundary-demo .ok { padding: 0.5rem 0.75rem; border-radius: 8px; border: 1px solid var(--accent); color: var(--accent); }
.boundary-demo .bad { padding: 0.5rem 0.75rem; border-radius: 8px; border: 1px solid #dc2626; color: #dc2626; }

.dual-wheel { display: flex; gap: 1rem; justify-content: center; flex-wrap: wrap; }
.dual-wheel .wheel {
  width: 88px; height: 88px; border-radius: 50%; display: grid; place-items: center;
  font-size: 0.85rem; font-weight: 600; border: 2px solid var(--border);
}
.dual-wheel .law { border-color: var(--accent); color: var(--accent); }
.dual-wheel .virtue { border-color: var(--accent-2); color: var(--accent-2); }

.site-footer {
  text-align: center; padding: 2rem 1rem; color: var(--muted); font-size: 0.82rem;
}
.site-footer a { color: var(--accent); }

@media (max-width: 600px) {
  .lesson-footer .btn {
    min-height: 44px;
    touch-action: manipulation;
    flex: 1 1 100%;
  }
}

.course-percent { font-size: 0.82rem; color: var(--accent); margin: 0.35rem 0 0.5rem; }
.demo-loading { text-align: center; padding: 2rem 1rem; }
@media (prefers-reduced-motion: reduce) {
  :root:not([data-motion="on"]) *, :root:not([data-motion="on"]) *::before, :root:not([data-motion="on"]) *::after { animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; transition-duration: 0.01ms !important; }
  :root:not([data-motion="on"]) .course-card:hover { transform: none; }
}

.demo-sliders { display: flex; flex-wrap: wrap; gap: 0.75rem; align-items: center; font-size: 0.85rem; color: var(--muted); margin-bottom: 0.5rem; width: 100%; }
.demo-sliders input[type=range] { width: min(180px, 46vw); accent-color: var(--accent); }
.pyth-svg, .tree-svg { width: 100%; max-height: 220px; }

.quiz-explain { font-size: 0.88rem; line-height: 1.55; margin: 0.5rem 0 0; padding: 0.65rem 0.85rem; border-radius: 10px; border: 1px solid var(--border); }
.quiz-explain.ok { background: rgba(15, 118, 110,0.08); color: var(--accent); }
.quiz-explain.bad { background: rgba(220, 38, 38,0.08); color: #dc2626; }
.quiz-choice.picked-wrong { border-color: rgba(220, 38, 38,0.5); }
.quiz-choice.picked-correct { border-color: rgba(15, 118, 110,0.45); }

.exam-point { font-size: 0.82rem; color: var(--accent); margin: 0.35rem 0 0; }
.step-tag { display: inline-flex; align-items: center; justify-content: center; width: 1.35rem; height: 1.35rem; border-radius: 999px; background: var(--surface-2); color: var(--accent); font-size: 0.72rem; margin-right: 0.45rem; }

@media (max-width: 480px) { .grid-subjects { grid-template-columns: 1fr; } .phase-columns { grid-template-columns: 1fr; } }

.lesson-shell.celebrate { animation: celebrate-pop calc(var(--dur-deliberate) * 2) var(--ease-standard); }
@keyframes celebrate-pop { 0% { box-shadow: 0 0 0 rgba(15, 118, 110,0); } 40% { box-shadow: 0 0 40px rgba(15, 118, 110,0.35); } 100% { box-shadow: var(--shadow); } }

.btn:focus-visible, .course-card:focus-visible, .quiz-choice:focus-within, .decompose-chip:focus-visible, .tl-node:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.timeline-rail { display: flex; flex-direction: column; gap: 0.5rem; }
.tl-node { text-align: left; border: 1px solid var(--border); background: var(--surface-2); color: var(--text); border-radius: 10px; padding: 0.55rem 0.75rem; cursor: pointer; }
.tl-node.on { border-color: var(--accent); color: var(--accent); }
.inline-toggle { margin-top: 0.5rem; }
.site-footer a { color: var(--accent); }

.decompose-tip { font-size: 0.78rem; margin: 0 0 0.5rem; line-height: 1.5; color: var(--muted); }
.decompose-tip kbd { font-size: 0.72rem; padding: 0.1rem 0.35rem; border-radius: 4px; border: 1px solid var(--border); background: var(--surface-2); color: var(--text); }
.decompose-controls {
  display: flex; flex-direction: column; gap: 0.5rem; width: 100%;
  margin-bottom: 0.65rem; padding: 0.65rem 0.7rem 0.7rem;
  border: 1px solid var(--border); border-radius: 12px; background: var(--surface);
}
.decompose-head { display: flex; align-items: center; justify-content: space-between; gap: 0.5rem; }
.decompose-label { font-size: 0.72rem; letter-spacing: 0.08em; text-transform: uppercase; color: var(--accent); }
.decompose-progress { font-size: 0.72rem; color: var(--muted); }
.decompose-learn-hint { margin: 0; font-size: 0.84rem; line-height: 1.5; color: var(--text); min-height: 2.4em; overflow-wrap: anywhere; }
.decompose-bar { display: flex; flex-wrap: wrap; gap: 0.4rem; }
.decompose-chip {
  font-size: 0.75rem; padding: 0.35rem 0.7rem; border-radius: 999px;
  border: 1px solid var(--border); background: var(--surface-2); color: var(--muted);
  cursor: pointer; min-height: 36px; touch-action: manipulation;
}
.decompose-chip.on { border-color: rgba(15, 118, 110,0.45); color: var(--accent); background: var(--accent-soft); }
.decompose-nav { display: flex; flex-wrap: wrap; align-items: center; gap: 0.4rem; }
.decompose-nav .btn { min-height: 44px; }
.decompose-kbd { font-size: 0.7rem; margin-left: auto; color: var(--muted); }
.demo-stage [data-layer].layer-off, .demo-stage .layer-off { opacity: 0.08 !important; visibility: hidden; pointer-events: none; }
.demo-stage [data-layer]:not(.layer-off), .demo-stage .seq-card:not(.layer-off) { transition: opacity var(--dur-base) var(--ease-decelerate), visibility var(--dur-base); }
.demo-stage [data-layer].layer-active, .demo-stage .seq-card.layer-active {
  filter: drop-shadow(0 0 8px rgba(15, 118, 110, 0.45));
}
.tree-links line { transition: opacity var(--dur-base); }

.earth-demo { position: relative; width: min(200px, 100%); min-height: 140px; }
.earth-demo .sun { position: absolute; left: 10%; top: 20%; width: 36px; height: 36px; border-radius: 50%; background: #b45309; box-shadow: 0 0 20px rgba(217, 119, 6,0.5); }
.earth-demo .axis { position: absolute; left: 45%; top: 15%; width: 2px; height: 100px; background: #64748b; transform: rotate(23deg); transform-origin: bottom center; }
.earth-demo .earth { position: absolute; left: 42%; top: 40%; width: 48px; height: 48px; border-radius: 50%; background: linear-gradient(135deg, #4f46e5, #0f766e); }

/* 课时学习面：讲解条 / 高亮 / 阶段条 / 闸门 / 演示区 · 窄屏与深色一致 */
.lesson-steps.interact li {
  padding: 0.4rem 0.55rem;
  border-radius: 8px;
}
.lesson-steps.interact li.done {
  background: var(--accent-soft);
}
.crumb { overflow-wrap: anywhere; }
.quiz-panel { color: var(--text); }
.quiz-panel legend { color: var(--text); }
.demo-caption { overflow-wrap: anywhere; }
.factory-demo { flex-wrap: wrap; }
.bond-demo { max-width: 100%; justify-content: center; }
.projectile-demo { max-width: 100%; }
.balance-demo .beam { width: min(200px, 100%); }
.highlight-sentence { overflow-wrap: anywhere; }

@media (max-width: 700px) {
  .lesson-shell { padding: 1rem 0.85rem; }
  .lesson-phase-nav {
    position: sticky;
    top: var(--sticky-offset);
    z-index: 4;
    margin: 0 -0.85rem 0.85rem;
    padding: 0.45rem 0.85rem 0.55rem;
    background: rgba(255, 255, 255, 0.94);
    backdrop-filter: blur(14px);
    border-bottom: 1px solid var(--border);
  }
  .explain-live {
    font-size: 0.92rem;
    padding: 0.8rem 0.85rem 0.85rem 0.95rem;
  }
  .lesson-steps.explain-sync li { padding: 0.55rem 0.7rem; }
  .quiz-gate { padding: 0.95rem 0.9rem; font-size: 0.9rem; }
}

@media (max-width: 600px) {
  main {
    padding: 0.9rem 0.85rem;
    padding-bottom: max(1.1rem, env(safe-area-inset-bottom));
  }
  .demo-stage {
    min-height: 180px;
    padding: 0.7rem;
    margin: 0.85rem 0;
    border-radius: 12px;
  }
  .demo-controls {
    flex-direction: column;
    align-items: stretch;
    gap: 0.55rem;
  }
  .demo-controls > .btn {
    flex: 1 1 calc(50% - 0.4rem);
    width: auto;
  }
  .demo-controls label,
  .demo-slider,
  .demo-sliders {
    width: 100%;
    flex-wrap: wrap;
  }
  .demo-controls input[type="range"],
  .demo-slider input[type="range"],
  .demo-sliders input[type="range"] {
    width: 100%;
    flex: 1 1 100%;
  }
  .decompose-kbd { display: none; }
  .decompose-nav {
    display: grid;
    grid-template-columns: 1fr 1fr;
    width: 100%;
  }
  .decompose-nav .btn { width: 100%; }
  .decompose-chip { min-height: 40px; }
  .demo-loading { padding: 1.4rem 0.5rem; }
  .english-demo .line { font-size: 1rem; overflow-wrap: anywhere; }
  .eq-demo span { font-size: 0.95rem; display: inline-block; overflow-wrap: anywhere; }
}

@media (hover: none) and (pointer: coarse) {
  .decompose-kbd { display: none; }
  .course-card:hover { transform: none; }
  .btn:hover { transform: none; }
}

.grade-band-nav { display: flex; gap: 0.5rem; flex-wrap: wrap; margin: 1rem 0; }
.grade-band-btn { padding: 0.45rem 0.9rem; border-radius: 999px; border: 1px solid var(--border, #cbd5e1); background: var(--surface, #ffffff); color: inherit; cursor: pointer; }
.grade-band-btn.active { background: #0f766e; color: #ffffff; border-color: #0f766e; }
.course-card[class*="elem-g"] .subject-badge { background: #b45309; color: #ffffff; }

/* 小学 stub：更大字、居中卡片、黄色强调。仅 .elem-stub 使用，不影响九科 demo */
.elem-stub {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.7rem;
  width: min(100%, 28rem);
  min-height: 12.5rem;
  margin: 0 auto;
  padding: 1.75rem 1.4rem 1.5rem;
  text-align: center;
  border-radius: 22px;
  border: 2px solid rgba(217, 119, 6, 0.5);
  background:
    radial-gradient(ellipse 75% 55% at 50% 0%, rgba(217, 119, 6, 0.24), transparent 68%),
    var(--surface-2);
  box-shadow:
    0 0 0 1px rgba(217, 119, 6, 0.12),
    0 14px 32px rgba(217, 119, 6, 0.12);
}
.elem-stub::before {
  content: "";
  width: 2.7rem;
  height: 2.7rem;
  border-radius: 50%;
  background: radial-gradient(circle at 34% 30%, #b45309, #b45309 58%, #d97706);
  box-shadow: 0 0 22px rgba(217, 119, 6, 0.55);
}
.elem-stub .elem-big {
  margin: 0;
  font-size: clamp(1.5rem, 4.4vw, 1.95rem);
  font-weight: 800;
  line-height: 1.3;
  letter-spacing: 0.01em;
  color: #b45309;
  text-align: center;
  padding: 0;
}
.elem-stub .demo-caption {
  margin: 0;
  max-width: 22ch;
  font-size: 1.08rem;
  line-height: 1.55;
  color: #b45309;
  opacity: 0.88;
}

/* 小学课时面：大字号、疏间距、黄色强调。id/class 双选择器，兼容 #view-lesson 与 .view-lesson */
.view-lesson[data-grade-band="elementary"],
#view-lesson[data-grade-band="elementary"],
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] {
  --accent: #b45309;
  --accent-2: #d97706;
  --on-accent: #ffffff;
  --accent-soft: rgba(217, 119, 6, 0.16);
  --accent-line: rgba(217, 119, 6, 0.42);
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-shell {
  padding: 1.5rem 1.35rem 1.6rem;
  border-color: rgba(217, 119, 6, 0.22);
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-nav {
  gap: 1rem;
  margin-bottom: 1.25rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .crumb {
  font-size: 1rem;
  line-height: 1.5;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-header h2 {
  font-size: clamp(1.45rem, 4vw, 1.9rem);
  line-height: 1.3;
  margin: 0 0 0.55rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-header .muted,
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-header #lesson-summary {
  font-size: 1.08rem;
  line-height: 1.65;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .exam-point {
  font-size: 1.05rem;
  margin-top: 0.55rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .review-status {
  font-size: 1rem;
  margin-top: 0.7rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-phase-nav {
  gap: 0.65rem;
  margin: 0.35rem 0 1.35rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-phase-nav .phase-chip {
  min-height: 52px;
  font-size: clamp(0.92rem, 3vw, 1.05rem);
  padding: 0.55rem 0.6rem;
  line-height: 1.3;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-phase-nav .phase-chip.active {
  border-color: rgba(217, 119, 6, 0.55);
  box-shadow: 0 0 0 1px rgba(217, 119, 6, 0.16);
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .phase-block {
  margin: 1.35rem 0;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .phase-block h3 {
  font-size: 1.12rem;
  margin: 0 0 0.7rem;
  color: #b45309;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .phase-block .muted,
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .decompose-tip {
  font-size: 1.02rem;
  line-height: 1.65;
  margin-bottom: 0.85rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .decompose-tip kbd {
  font-size: 0.9rem;
  padding: 0.15rem 0.45rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .decompose-kbd {
  display: none;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .demo-stage {
  min-height: 260px;
  margin: 1.15rem 0 1.25rem;
  padding: 1.25rem;
  border-radius: 18px;
  border-color: rgba(217, 119, 6, 0.28);
  background:
    radial-gradient(ellipse 80% 50% at 50% 0%, rgba(217, 119, 6, 0.14), transparent 62%),
    linear-gradient(180deg, var(--surface-2), var(--bg));
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .demo-stage [data-layer].layer-active,
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .demo-stage .seq-card.layer-active {
  filter: drop-shadow(0 0 10px rgba(217, 119, 6, 0.5));
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .demo-controls {
  gap: 0.9rem;
  margin-bottom: 1.2rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .demo-controls label,
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .demo-slider,
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .demo-sliders {
  font-size: 1.02rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .decompose-controls {
  gap: 0.7rem;
  padding: 0.85rem 0.85rem 0.95rem;
  margin-bottom: 0.85rem;
  border-color: rgba(217, 119, 6, 0.22);
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .decompose-label,
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .decompose-progress {
  font-size: 0.88rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .decompose-learn-hint {
  font-size: 1.05rem;
  line-height: 1.55;
  min-height: 2.6em;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .decompose-chip {
  font-size: 0.95rem;
  padding: 0.45rem 0.9rem;
  min-height: 44px;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .decompose-chip.on {
  border-color: rgba(217, 119, 6, 0.5);
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .explain-live {
  margin: 1rem 0 0.35rem;
  padding: 0.95rem 1rem 1rem 1.1rem;
  font-size: 1.08rem;
  line-height: 1.6;
  min-height: 3.2em;
  border-left-width: 4px;
  background: linear-gradient(90deg, rgba(217, 119, 6, 0.16), rgba(245, 158, 11, 0.05));
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .explain-live::before {
  font-size: 0.78rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-steps {
  font-size: 1.08rem;
  line-height: 1.7;
  padding-left: 1.35rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-steps li {
  margin-bottom: 0.7rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-steps.explain-sync {
  gap: 0.55rem;
  padding-left: 0;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-steps.explain-sync li {
  padding: 0.7rem 0.85rem;
  border-radius: 12px;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-steps.explain-sync li.active {
  box-shadow: inset 0 0 0 1px rgba(217, 119, 6, 0.12);
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-steps.interact li {
  padding: 0.55rem 0.7rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .step-tag {
  width: 1.65rem;
  height: 1.65rem;
  font-size: 0.88rem;
  margin-right: 0.55rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .quiz-gate {
  margin: 1.15rem 0 0.7rem;
  padding: 1.1rem 1.05rem;
  font-size: 1.05rem;
  line-height: 1.65;
  border-left-color: var(--accent-2);
  border-color: rgba(217, 119, 6, 0.28);
  background: linear-gradient(180deg, rgba(217, 119, 6, 0.1), var(--surface-2));
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .quiz-panel {
  margin: 1.15rem 0;
  padding: 1.15rem 1.05rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .quiz-panel legend {
  font-size: 1.12rem;
  margin-bottom: 0.8rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .quiz-choice {
  margin: 0.5rem 0;
  padding: 0.85rem 1rem;
  font-size: 1.05rem;
  min-height: 52px;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .quiz-choice.picked-correct {
  border-color: rgba(217, 119, 6, 0.5);
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .quiz-feedback,
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .quiz-explain {
  font-size: 1.05rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .quiz-explain.ok {
  background: rgba(217, 119, 6, 0.1);
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .btn {
  min-height: 48px;
  font-size: 1.05rem;
  padding: 0.7rem 1.15rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .btn.primary {
  background: linear-gradient(135deg, #b45309, #d97706);
  color: var(--on-accent);
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-footer {
  gap: 0.8rem;
  margin-top: 1.5rem;
}
:is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-shell.celebrate {
  animation: elem-celebrate-pop calc(var(--dur-deliberate) * 2) var(--ease-standard);
}
@keyframes elem-celebrate-pop {
  0% { box-shadow: 0 0 0 rgba(217, 119, 6, 0); }
  40% { box-shadow: 0 0 40px rgba(217, 119, 6, 0.4); }
  100% { box-shadow: var(--shadow); }
}

@media (max-width: 700px) {
  :is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-shell {
    padding: 1.2rem 0.95rem 1.35rem;
  }
  :is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .lesson-phase-nav {
    margin: 0 -0.95rem 1.1rem;
    padding: 0.5rem 0.95rem 0.65rem;
  }
}

@media (max-width: 600px) {
  :is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .demo-stage {
    min-height: 220px;
    padding: 1rem;
    margin: 1rem 0;
    border-radius: 16px;
  }
  :is(#view-lesson, .view-lesson)[data-grade-band="elementary"] .elem-stub {
    min-height: 11rem;
    padding: 1.35rem 1rem 1.2rem;
  }
}

/* —— 个性化：主题色经 :root 自定义属性下发（src/prefs.mjs themeCssVars），小学课时面仍用自己的黄色 —— */
body {
  background:
    radial-gradient(ellipse 80% 50% at 50% -20%, var(--accent-haze, rgba(15, 118, 110, 0.12)), transparent),
    radial-gradient(ellipse 60% 40% at 100% 0%, rgba(99, 102, 241, 0.1), transparent),
    var(--bg);
}
.brand-mark { box-shadow: 0 0 24px var(--accent-glow, rgba(15, 118, 110, 0.35)); }
.btn.primary { background: linear-gradient(135deg, var(--accent), var(--accent-deep, #115e59)); }
.course-card:hover { border-color: var(--accent-line); }
.chip.done { border-color: var(--accent-line); }
.lesson-shell.celebrate { animation-name: celebrate-pop-theme; }
@keyframes celebrate-pop-theme {
  0% { box-shadow: 0 0 0 transparent; }
  40% { box-shadow: 0 0 40px var(--accent-glow, rgba(15, 118, 110, 0.35)); }
  100% { box-shadow: var(--shadow); }
}

.topbar-meta { display: flex; align-items: center; gap: 0.5rem; }
.btn-personalize {
  min-height: 34px; padding: 0.3rem 0.75rem; border-radius: 999px; font-size: 0.78rem;
  display: inline-flex; align-items: center; gap: 0.4rem;
}
.btn-personalize::before {
  content: ''; width: 0.8rem; height: 0.8rem; border-radius: 50%;
  background: conic-gradient(var(--accent), var(--accent-2), var(--accent-deep, var(--accent)), var(--accent));
  box-shadow: 0 0 8px var(--accent-glow, transparent);
  transition: transform var(--dur-slow) var(--ease-spring);
}
.btn-personalize:hover::before { transform: rotate(120deg) scale(1.15); }

.hero-greet { display: flex; align-items: center; flex-wrap: wrap; gap: 0.4rem 0.75rem; }
.hero-greeting {
  margin: 0; font-size: 1.05rem; font-weight: 650; letter-spacing: 0.02em;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero-greeting:empty { display: none; }
.hero-line { margin: 0.25rem 0 0.5rem; color: var(--muted); font-size: 0.9rem; }
.hero-line:empty { display: none; }
.streak-chip {
  display: inline-flex; align-items: center; gap: 0.4rem;
  font-size: 0.75rem; padding: 0.2rem 0.65rem; border-radius: 999px;
  color: var(--accent); background: var(--accent-soft); border: 1px solid var(--accent-line);
}
.streak-chip[hidden] { display: none; }
.streak-chip::before {
  content: ''; width: 0.5rem; height: 0.5rem; border-radius: 50%;
  background: var(--accent); box-shadow: 0 0 6px var(--accent-glow, transparent);
}
.streak-chip.hot::before { animation: streak-spark calc(var(--dur-deliberate) * 2.9) var(--ease-standard) infinite; }
@keyframes streak-spark { 0%, 100% { transform: scale(1); opacity: 1; } 50% { transform: scale(1.55); opacity: 0.55; } }
@media (forced-colors: active) {
  .hero-greeting { background: none; color: CanvasText; }
}

.prefs-dialog {
  width: min(440px, calc(100vw - 2rem)); padding: 0; color: var(--text);
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow);
}
.prefs-dialog::backdrop { background: rgba(15, 23, 42, 0.35); backdrop-filter: blur(4px); }
.prefs-dialog[open] { animation: dialog-in var(--dur-base) var(--ease-decelerate); }
@keyframes dialog-in { from { opacity: 0; transform: translateY(14px) scale(0.97); } to { opacity: 1; transform: none; } }
.prefs-form { display: grid; gap: 1rem; padding: 1.25rem; }
.prefs-form h2 { margin: 0; font-size: 1.05rem; }
.prefs-field { display: grid; gap: 0.5rem; margin: 0; padding: 0; border: 0; min-width: 0; }
.prefs-field > span, .prefs-field legend { padding: 0; font-size: 0.82rem; color: var(--muted); }
.prefs-field input[type="text"], .prefs-field input[type="password"], .prefs-field input:not([type]) {
  font: inherit; color: var(--text); background: var(--surface-2);
  border: 1px solid var(--border); border-radius: 10px; padding: 0.6rem 0.75rem;
}
.prefs-field input:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
.swatches { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 0.5rem; }
.swatch, .seg label {
  position: relative; display: flex; align-items: center; gap: 0.45rem; cursor: pointer;
  min-height: 44px; min-width: 44px; touch-action: manipulation;
  padding: 0.5rem 0.6rem; font-size: 0.85rem; border-radius: 10px;
  background: var(--surface-2); border: 1px solid var(--border);
  transition: border-color var(--dur-fast), transform var(--dur-fast), background var(--dur-fast);
}
.swatch:hover, .seg label:hover { transform: translateY(-1px); }
.swatch input, .seg input { position: absolute; opacity: 0; pointer-events: none; }
.swatch-dot {
  flex: none; width: 1.15rem; height: 1.15rem; border-radius: 50%;
  background: linear-gradient(135deg, var(--sw-a), var(--sw-b)); box-shadow: 0 0 0 2px var(--surface);
}
.swatch:has(input:checked) { border-color: var(--sw-a); box-shadow: inset 0 0 0 1px var(--sw-a); }
.swatch:has(input:checked) .swatch-dot { animation: fx-pop var(--dur-slow) var(--ease-spring); }
.seg { display: flex; flex-wrap: wrap; gap: 0.45rem; }
.seg label:has(input:checked) { color: var(--accent); border-color: var(--accent-line); background: var(--accent-soft); }
.swatch:has(input:focus-visible), .seg label:has(input:focus-visible) { outline: 2px solid var(--accent); outline-offset: 2px; }
.prefs-actions { display: flex; align-items: center; justify-content: space-between; gap: 0.75rem; }
.prefs-note { margin: 0; font-size: 0.75rem; color: var(--muted); }

/* —— 交互动效（app/motion.mjs）：进场、错峰、光斑倾斜、水波纹、彩纸、答题反馈 —— */
.view-enter { animation: view-rise var(--dur-slow) var(--ease-decelerate) both; }
@keyframes view-rise { from { opacity: 0.55; transform: translateY(10px); } to { opacity: 1; transform: none; } }
.stagger-in { animation: card-in var(--dur-slow) var(--ease-decelerate) both; animation-delay: calc(var(--i, 0) * var(--stagger-step)); }
@keyframes card-in { from { opacity: 0.35; transform: translateY(16px) scale(0.97); } to { opacity: 1; transform: none; } }

.course-card::after {
  content: ''; position: absolute; inset: 0; border-radius: inherit; pointer-events: none;
  opacity: 0; transition: opacity var(--dur-base);
  background: radial-gradient(240px circle at var(--mx, 50%) var(--my, 50%), var(--accent-spot, rgba(15, 118, 110, 0.18)), transparent 70%);
}
.course-card.is-lit::after { opacity: 1; }
.course-card.is-lit {
  border-color: var(--accent-line);
  transform: perspective(900px) rotateX(var(--rx, 0deg)) rotateY(var(--ry, 0deg)) translateY(-3px);
  transition: transform var(--dur-instant) var(--ease-decelerate), border-color var(--dur-base);
}

.btn { position: relative; overflow: hidden; isolation: isolate; }
.fx-ripple {
  position: absolute; z-index: -1; border-radius: 50%; pointer-events: none;
  background: currentColor; opacity: 0.25; transform: scale(0);
  animation: fx-ripple var(--dur-deliberate) var(--ease-decelerate) forwards;
}
@keyframes fx-ripple { to { transform: scale(1); opacity: 0; } }

.fx-burst { position: fixed; z-index: 30; width: 0; height: 0; pointer-events: none; }
.fx-burst i {
  position: absolute; left: -4px; top: -6px; width: 8px; height: 12px; border-radius: 2px;
  background: var(--hue, var(--accent));
  animation: confetti-fly calc(var(--dur-deliberate) * 1.7) var(--ease-decelerate) forwards;
}
@keyframes confetti-fly {
  0% { transform: translate(0, 0) rotate(0deg); opacity: 1; }
  100% { transform: translate(var(--dx, 0px), calc(var(--dy, 0px) + 64px)) rotate(var(--rot, 180deg)); opacity: 0; }
}

.fx-pop { animation: fx-pop var(--dur-slow) var(--ease-spring); }
@keyframes fx-pop { 0% { transform: scale(0.94); } 60% { transform: scale(1.05); } 100% { transform: scale(1); } }
.fx-shake { animation: fx-shake var(--dur-slow) var(--ease-standard); }
@keyframes fx-shake {
  0%, 100% { transform: translateX(0); }
  20% { transform: translateX(-6px); }
  40% { transform: translateX(5px); }
  60% { transform: translateX(-3px); }
  80% { transform: translateX(2px); }
}

/* 用户在「个性化」里关掉动效：不看系统偏好，一律静止。 */
:root[data-motion="off"] *, :root[data-motion="off"] *::before, :root[data-motion="off"] *::after {
  animation-duration: 0.01ms !important; animation-delay: 0s !important; animation-iteration-count: 1 !important;
  transition-duration: 0.01ms !important; scroll-behavior: auto !important;
}
:root[data-motion="off"] .course-card:hover, :root[data-motion="off"] .course-card.is-lit { transform: none; }

/* —— 壳层交互（动效交互重构 P2）：视图过渡、解锁提示、离屏卡片 —— */
::view-transition-old(root), ::view-transition-new(root) { animation-duration: var(--dur-slow); animation-timing-function: var(--ease-decelerate); }
::view-transition-group(lesson-title) { animation-duration: var(--dur-slow); animation-timing-function: var(--ease-decelerate); }
.quiz-nudge {
  position: fixed; left: 50%; bottom: calc(1rem + env(safe-area-inset-bottom, 0px)); z-index: 20;
  transform: translateX(-50%);
  padding: 0.7rem 1.25rem; border: 0; border-radius: 999px; cursor: pointer;
  font: inherit; font-weight: 600; color: var(--on-accent);
  background: linear-gradient(135deg, var(--accent), var(--accent-deep, var(--accent)));
  box-shadow: 0 10px 30px rgba(15, 23, 42, 0.12), 0 0 0 1px var(--accent-line);
  animation: nudge-in var(--dur-slow) var(--ease-spring) both;
}
.quiz-nudge[hidden] { display: none; }
.quiz-nudge:focus-visible { outline: 2px solid var(--text); outline-offset: 3px; }
@keyframes nudge-in { from { opacity: 0; transform: translate(-50%, 12px) scale(0.96); } to { opacity: 1; transform: translate(-50%, 0) scale(1); } }
.update-toast { bottom: calc(4.5rem + env(safe-area-inset-bottom, 0px)); }
.lesson-title-focus:focus { outline: none; }
.lesson-title-focus:focus-visible { outline: 2px solid var(--accent); outline-offset: 4px; border-radius: 6px; }

/* —— 学习流程 R2（docs/学习流程重构设计.md §五）：今日、首次进入、课程地图、错题本、手机触控 —— */
.hero { margin-bottom: 1rem; }
.today {
  margin-bottom: 1.5rem; padding: 1rem; border-radius: var(--radius);
  background: var(--surface); border: 1px solid var(--border); box-shadow: var(--shadow);
}
.today-head { display: flex; align-items: center; justify-content: space-between; gap: 0.75rem; margin-bottom: 0.75rem; }
.today-titles { min-width: 0; }
.today-head h2 { margin: 0; font-size: 1.15rem; }
.today-sub { margin: 0.2rem 0 0; font-size: 0.85rem; color: var(--muted); }
.today-sub:empty { display: none; }
.goal-ring { position: relative; flex: none; width: 56px; height: 56px; display: grid; place-items: center; }
.goal-ring[hidden], .onboard[hidden], .today-list[hidden], .today-links[hidden] { display: none; }
.goal-ring svg { position: absolute; inset: 0; width: 100%; height: 100%; transform: rotate(-90deg); }
.goal-ring circle { fill: none; stroke-width: 3.5; }
.ring-track { stroke: var(--surface-2); }
.ring-fill {
  stroke: var(--accent); stroke-linecap: round; stroke-dasharray: 0 100;
  transition: stroke-dasharray var(--dur-slow) var(--ease-decelerate);
}
.goal-ring.is-full .ring-fill { filter: drop-shadow(0 0 4px var(--accent-glow, rgba(15, 118, 110, 0.35))); }
.goal-ring.is-empty .ring-fill { stroke-opacity: 0; }
.btn-personalize { white-space: nowrap; }
.ring-text { position: relative; font-size: 0.82rem; font-weight: 650; }

.today-list { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.5rem; }
.task-card {
  width: 100%; min-height: 56px; display: flex; align-items: center; gap: 0.75rem;
  padding: 0.7rem 0.85rem; border-radius: 12px; cursor: pointer; text-align: left; touch-action: manipulation;
  font: inherit; color: var(--text); background: var(--surface-2); border: 1px solid var(--border);
  transition: border-color var(--dur-fast), transform var(--dur-fast) var(--ease-decelerate);
}
.task-card:hover { border-color: var(--accent-line); transform: translateY(-1px); }
.task-card:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.task-kind {
  flex: none; min-width: 2.6rem; padding: 0.2rem 0.45rem; border-radius: 8px; text-align: center;
  font-size: 0.75rem; font-weight: 650; color: var(--accent); background: var(--accent-soft); border: 1px solid var(--accent-line);
}
.task-review .task-kind { color: #b45309; background: rgba(217, 119, 6, 0.1); border-color: rgba(217, 119, 6, 0.35); }
.task-continue .task-kind { color: var(--accent-2); background: rgba(79, 70, 229, 0.12); border-color: rgba(79, 70, 229, 0.35); }
.task-body { flex: 1; min-width: 0; display: grid; gap: 0.15rem; }
.task-title { font-weight: 600; overflow-wrap: anywhere; }
.task-meta { font-size: 0.78rem; color: var(--muted); }
.task-go { flex: none; font-size: 1.3rem; line-height: 1; color: var(--muted); }
.today-done, .today-empty { padding: 0.6rem 0.85rem; border-radius: 12px; font-size: 0.88rem; }
.today-done { color: var(--accent); background: var(--accent-soft); border: 1px dashed var(--accent-line); }
.today-empty { color: var(--muted); background: var(--surface-2); }
.today-links { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: 0.75rem; }
.today-links .btn { flex: 1 1 auto; }
.count-badge {
  display: inline-grid; place-items: center; min-width: 1.35rem; height: 1.35rem; padding: 0 0.3rem; margin-left: 0.25rem;
  border-radius: 999px; font-size: 0.72rem; font-weight: 700; color: #1f0a0e; background: #fb7185;
}
.count-badge:empty { display: none; }

.onboard { display: grid; gap: 0.75rem; }
.ob-step { margin: 0; font-size: 0.78rem; color: var(--accent); letter-spacing: 0.04em; }
.ob-q { margin: 0.25rem 0 0; font-size: 1rem; }
.ob-q small { margin-left: 0.5rem; font-size: 0.78rem; font-weight: 400; color: var(--muted); }
.ob-options { display: grid; grid-template-columns: repeat(auto-fill, minmax(8.5rem, 1fr)); gap: 0.5rem; }
.ob-grades, .ob-subjects { grid-template-columns: repeat(auto-fill, minmax(5.5rem, 1fr)); }
.ob-opt {
  min-height: 48px; padding: 0.55rem 0.75rem; border-radius: 12px; cursor: pointer; touch-action: manipulation;
  font: inherit; font-size: 0.92rem; color: var(--text); background: var(--surface-2); border: 1px solid var(--border);
  transition: border-color var(--dur-fast), background var(--dur-fast), transform var(--dur-fast) var(--ease-spring);
}
.ob-opt:hover { border-color: var(--accent-line); }
.ob-opt:active { transform: scale(0.97); }
.ob-opt[aria-pressed="true"] { color: var(--accent); background: var(--accent-soft); border-color: var(--accent); font-weight: 650; }
.ob-opt:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.ob-note { margin: 0; font-size: 0.8rem; color: var(--muted); }
.ob-actions { display: flex; justify-content: space-between; gap: 0.5rem; margin-top: 0.25rem; }
.ob-actions .btn.primary { flex: 1; max-width: 16rem; }

.card-map { display: none; width: 100%; margin-top: 0.85rem; }

.study-dialog { width: min(560px, calc(100vw - 1.5rem)); max-height: min(86vh, 760px); }
.study-form { display: grid; grid-template-rows: auto 1fr; max-height: inherit; }
.study-head { display: flex; align-items: center; justify-content: space-between; gap: 0.75rem; padding: 1rem 1.1rem 0.5rem; }
.study-head h2 { margin: 0; font-size: 1.05rem; }
.study-body { overflow: auto; padding: 0.25rem 1.1rem 1.1rem; overscroll-behavior: contain; }
.map-pick { display: grid; gap: 0.35rem; margin-bottom: 0.75rem; font-size: 0.82rem; color: var(--muted); }
.map-pick select {
  min-height: 44px; padding: 0.5rem 0.65rem; border-radius: 10px;
  font: inherit; font-size: 1rem; color: var(--text); background: var(--surface-2); border: 1px solid var(--border);
}
.map-list, .mk-list { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.4rem; }
.map-row {
  width: 100%; min-height: 52px; display: flex; align-items: center; gap: 0.65rem; padding: 0.55rem 0.7rem;
  border-radius: 12px; cursor: pointer; text-align: left; font: inherit; color: var(--text);
  background: var(--surface-2); border: 1px solid var(--border); transition: border-color var(--dur-fast);
}
.map-row:hover { border-color: var(--accent-line); }
.map-row.is-due { border-color: rgba(217, 119, 6, 0.45); }
.map-row:focus-visible, .map-pick select:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.map-idx {
  flex: none; width: 1.8rem; height: 1.8rem; display: grid; place-items: center; border-radius: 50%;
  font-size: 0.8rem; color: var(--muted); background: var(--surface);
}
.map-main, .mk-main { flex: 1; min-width: 0; display: grid; gap: 0.1rem; }
.map-title, .mk-title { overflow-wrap: anywhere; }
.map-due { font-size: 0.75rem; color: #b45309; }
.map-min { font-size: 0.72rem; color: var(--muted); }
.map-length { margin: 0 0 0.6rem; font-size: 0.82rem; }
.map-units { display: grid; gap: 0.9rem; }
.map-unit h3 { margin: 0 0 0.4rem; font-size: 0.8rem; font-weight: 600; color: var(--muted); letter-spacing: 0.02em; }
.lesson-place { margin: 0 0 0.25rem; font-size: 0.78rem; color: var(--muted); }
/* 分钟放在步名下面一行；两段各自不折行（窄屏曾把「① 看」「3 分」各拆成两行） */
.lesson-phase-nav .phase-chip { flex-direction: column; gap: 0.05rem; white-space: nowrap; }
.lesson-phase-nav .phase-min { display: block; font-size: 0.8em; font-weight: 400; opacity: 0.8; line-height: 1.1; }
.lesson-phase-nav .phase-min:empty { display: none; }
.badge { flex: none; padding: 0.15rem 0.5rem; border-radius: 999px; font-size: 0.72rem; color: var(--muted); border: 1px solid var(--border); }
.badge-learning { color: var(--accent-2); border-color: rgba(79, 70, 229, 0.4); }
.badge-shaky { color: #b45309; border-color: rgba(217, 119, 6, 0.45); }
.badge-mastered { color: var(--accent); border-color: var(--accent-line); }
.badge-retained { color: var(--on-accent); background: var(--accent); border-color: var(--accent); }
.mk-group + .mk-group { margin-top: 1rem; }
.mk-group h3 { margin: 0 0 0.5rem; font-size: 0.88rem; color: var(--muted); }
.mk-row {
  display: flex; align-items: center; gap: 0.75rem; padding: 0.55rem 0.7rem; border-radius: 12px;
  background: var(--surface-2); border: 1px solid var(--border);
}
.mk-main small { font-size: 0.75rem; color: var(--muted); }
.mk-redo { flex: none; }
.study-empty { margin: 0.5rem 0 0; color: var(--muted); line-height: 1.6; }

.about { margin-top: 2rem; padding-top: 1rem; border-top: 1px solid var(--border); }
.about h2 { margin: 0.25rem 0; font-size: 1rem; }
.about .lead { margin: 0.35rem 0 0; font-size: 0.85rem; }

/* 触屏与手机：可点元素 ≥44×44px；手机上课时芯片收起，改走「课程地图」 */
@media (pointer: coarse) {
  .chip { min-height: 44px; display: inline-flex; align-items: center; padding: 0.3rem 0.75rem; font-size: 0.8rem; }
  .btn-personalize, .grade-band-btn { min-height: 44px; }
}
@media (max-width: 480px) {
  .btn-personalize, .grade-band-btn { min-height: 44px; }
  .tagline { display: none; }
  .brand-mark { width: 34px; height: 34px; border-radius: 10px; }
  .topbar-meta .pill { font-size: 0.72rem; }
  .grade-band-nav { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .lesson-chips { display: none; }
  .card-map { display: flex; justify-content: center; }
  .today { padding: 0.85rem; }
  .ob-options { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .ob-grades, .ob-subjects { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .ob-actions .btn { flex: 1; }
  .site-footer a { display: inline-flex; align-items: center; min-height: 44px; padding: 0 0.25rem; }
  .study-dialog { width: 100vw; max-width: 100vw; max-height: 92vh; margin: auto 0 0; border-radius: var(--radius) var(--radius) 0 0; }
  .study-body { padding-bottom: max(1.1rem, env(safe-area-inset-bottom)); }
}

/* —— 学习流程 R3：课时四步（看 / 动 / 测 / 结），一次只显示当前步；手机上操作栏钉在底部 —— */
.lesson-phase-nav { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.lesson-phase-nav .phase-chip { cursor: pointer; }
.lesson-phase-nav .phase-chip.locked { opacity: 0.5; cursor: not-allowed; }
.lesson-shell[data-step] .phase-block { display: none; }
.lesson-shell[data-step="watch"] .phase-demo,
.lesson-shell[data-step="do"] .phase-demo,
.lesson-shell[data-step="do"] .phase-interact,
.lesson-shell[data-step="test"] .phase-quiz,
.lesson-shell[data-step="sum"] .phase-summary { display: block; }
.lesson-shell[data-step="do"] .phase-demo > h3,
.lesson-shell[data-step="do"] .decompose-tip,
.lesson-shell[data-step="do"] .explain-block { display: none; }
.phase-block h3:focus { outline: none; }
.phase-block h3:focus-visible { outline: 2px solid var(--accent); outline-offset: 4px; border-radius: 6px; }
.quiz-panel fieldset:disabled .quiz-choice { cursor: default; opacity: 0.7; }
.quiz-panel fieldset:disabled .quiz-choice.picked-wrong { opacity: 1; }
.quiz-retry { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: 0.75rem; }
.quiz-retry[hidden] { display: none; }
.summary-body { display: grid; gap: 0.6rem; }
.summary-head { display: flex; align-items: center; flex-wrap: wrap; gap: 0.6rem; margin: 0; font-size: 1.05rem; }
.summary-next { margin: 0; font-weight: 600; color: #b45309; }
.summary-note { margin: 0; font-size: 0.85rem; color: var(--muted); }
.summary-caption { margin: 0.4rem 0 0; font-size: 0.82rem; color: var(--muted); }
.summary-points { margin: 0; padding-left: 1.25rem; display: grid; gap: 0.35rem; line-height: 1.6; }
.summary-exam { margin: 0; font-size: 0.85rem; line-height: 1.55; color: #b45309; }
.summary-pitfalls { margin: 0; padding-left: 1.25rem; display: grid; gap: 0.35rem; line-height: 1.6; color: #e11d48; }
.lesson-footer { justify-content: space-between; }
.lesson-footer .btn[hidden] { display: none; }
#btn-step-next { flex: 1 1 auto; max-width: 22rem; margin-left: auto; }

@media (max-width: 600px) {
  .lesson-footer {
    position: sticky; bottom: 0; z-index: 4; flex-wrap: nowrap;
    margin: 1rem -0.85rem -1rem; padding: 0.6rem 0.85rem max(0.6rem, env(safe-area-inset-bottom));
    background: rgba(255, 255, 255, 0.94); backdrop-filter: blur(14px); border-top: 1px solid var(--border);
  }
  .lesson-footer .btn { flex: 0 1 auto; }
  #btn-step-next { flex: 1 1 auto; max-width: none; }
  .decompose-chip { min-height: 44px; }
}

/* —— 学习流程 R4：学习报告（四个数 + 七日柱 + 各科掌握条）、进度备份 —— */
.rp-caption { margin: 0.25rem 0 0.5rem; font-size: 0.82rem; color: var(--muted); }
.rp-stats { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 0.5rem; }
.rp-stat {
  display: grid; gap: 0.15rem; padding: 0.6rem 0.5rem; border-radius: 12px; text-align: center;
  background: var(--surface-2); border: 1px solid var(--border);
}
.rp-stat strong { font-size: 1.35rem; color: var(--accent); font-variant-numeric: tabular-nums; }
.rp-stat span { font-size: 0.75rem; color: var(--muted); }
.rp-days {
  list-style: none; margin: 0.9rem 0 1rem; padding: 0;
  display: grid; grid-template-columns: repeat(7, minmax(0, 1fr)); gap: 0.4rem; align-items: end;
}
.rp-day { display: grid; gap: 0.3rem; justify-items: center; }
.rp-bar { width: 100%; max-width: 2.2rem; height: 4.5rem; display: flex; align-items: flex-end; border-radius: 8px; background: var(--surface-2); overflow: hidden; }
.rp-bar > span { width: 100%; border-radius: 8px 8px 0 0; background: linear-gradient(180deg, var(--accent), var(--accent-2)); }
.rp-wd { font-size: 0.75rem; color: var(--muted); }
.rp-day.is-active .rp-wd { color: var(--text); font-weight: 650; }
.rp-subjects { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.45rem; }
.rp-subject { display: grid; grid-template-columns: minmax(0, 7.5rem) 1fr auto; align-items: center; gap: 0.6rem; font-size: 0.85rem; }
.rp-sub-name { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.rp-sub-bar { height: 8px; border-radius: 999px; background: var(--surface-2); overflow: hidden; }
.rp-sub-bar > span { display: block; height: 100%; border-radius: inherit; background: var(--accent); }
.rp-sub-num { font-size: 0.78rem; color: var(--muted); font-variant-numeric: tabular-nums; }
.rp-foot { margin: 1rem 0 0; font-size: 0.78rem; color: var(--muted); line-height: 1.6; }
.backup-actions { display: flex; flex-wrap: wrap; gap: 0.5rem; }
.backup-actions .btn { flex: 1 1 8rem; min-height: 44px; }
.import-confirm {
  display: grid; gap: 0.5rem; padding: 0.65rem 0.75rem; border-radius: 12px;
  background: var(--surface-2); border: 1px solid rgba(217, 119, 6, 0.45);
}
.import-confirm[hidden] { display: none; }
.import-confirm p { margin: 0; font-size: 0.85rem; line-height: 1.55; }
.backup-status { margin: 0; font-size: 0.8rem; color: var(--accent); }
.backup-status:empty { display: none; }
.backup-status.bad { color: #be123c; }
@media (max-width: 480px) {
  .rp-stats { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

/* —— 课时导览（docs/课程与双端设计.md §2.3）：抬头一句目标、①层路线、②任务卡 —— */
.lesson-goal {
  margin: 0.4rem 0 0; padding: 0.5rem 0.75rem; border-radius: 10px;
  background: var(--accent-soft); border-left: 3px solid var(--accent);
  font-size: 0.95rem; font-weight: 600; line-height: 1.55; color: var(--text);
}
.lesson-goal[hidden], .layer-route[hidden], .task-brief[hidden] { display: none; }
.lesson-summary { font-size: 0.85rem; margin: 0.35rem 0 0; }
.layer-route {
  margin: 0 0 0.5rem; font-size: 0.9rem; font-weight: 600; color: var(--accent);
}
.task-brief {
  margin: 0 0 0.75rem; padding: 0.7rem 0.85rem; border-radius: 12px;
  background: var(--surface); border: 1.5px solid var(--accent-line); box-shadow: var(--shadow);
}
.task-brief-label { margin: 0 0 0.2rem; font-size: 0.75rem; font-weight: 700; letter-spacing: 0.04em; color: var(--accent); }
.task-brief-text { margin: 0; font-size: 1rem; line-height: 1.6; color: var(--text); }
.interact-caption { margin: 0.5rem 0 0.25rem; font-size: 0.78rem; }

/* —— 账号与同步（docs/课程与双端设计.md §二） —— */
.btn-account { white-space: nowrap; max-width: 14rem; overflow: hidden; text-overflow: ellipsis; flex: none; }
.btn-account[hidden] { display: none; }
.btn-account.is-signed { border-color: var(--accent-line); color: var(--accent); }
.btn-account.is-error { border-color: rgba(190, 18, 60, 0.45); color: #be123c; }
.account-body { display: grid; gap: 0.75rem; }
.acct-form { display: grid; gap: 0.75rem; }
.acct-form input { min-height: 44px; font-size: 16px; }
.acct-line { margin: 0; }
.acct-status { margin: 0; font-size: 0.85rem; color: var(--accent); }
.acct-status:empty { display: none; }
.acct-status.bad { color: #be123c; }
/* 不可撤销的操作（注销 / 删号）：红色，白底对比 ≥ 4.5:1 */
.btn.danger { color: #be123c; border-color: rgba(190, 18, 60, 0.45); }
.btn.primary.danger { background: #be123c; color: #fff; border-color: #be123c; }
.acct-danger { margin-top: 0.5rem; padding-top: 0.75rem; border-top: 1px solid var(--line, rgba(15, 23, 42, 0.12)); display: grid; gap: 0.5rem; }
.acct-danger summary { cursor: pointer; font-size: 0.85rem; color: var(--muted, #475569); }
@media (max-width: 480px) {
  .btn-account { max-width: 8.5rem; }
}