.lesson-shell {
  min-height: 100vh;
}

.lesson-hero {
  width: min(1720px, calc(100% - 36px));
  margin: 24px auto 0;
  border: 1px solid rgba(255, 255, 255, 0.75);
  border-radius: 38px;
  background:
    linear-gradient(120deg, rgba(255, 255, 255, 0.92), rgba(255, 255, 251, 0.82)),
    repeating-linear-gradient(135deg, rgba(20, 33, 28, 0.04) 0 1px, transparent 1px 18px);
  box-shadow: var(--shadow);
}

.lesson-hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(320px, 0.55fr);
  gap: clamp(24px, 4vw, 60px);
  padding: 18px clamp(22px, 5vw, 72px) 52px;
}

.lesson-hero h1 {
  max-width: 820px;
  font-size: clamp(2.4rem, 4.4vw, 5.1rem);
}

.lesson-progress-card {
  border-radius: 32px;
  background:
    radial-gradient(circle at 88% 0%, rgba(248, 196, 93, 0.34), transparent 16rem),
    #14211c;
  color: white;
  padding: clamp(24px, 3vw, 38px);
}

.lesson-progress-card h2 {
  margin-top: 24px;
  color: white;
  font-size: clamp(1.9rem, 3vw, 3rem);
}

.lesson-progress-card ol {
  display: grid;
  gap: 12px;
  margin: 20px 0 0;
  padding: 0;
  list-style: none;
}

.lesson-progress-card li {
  border-radius: 18px;
  background: rgba(255, 255, 255, 0.08);
  padding: 14px 16px;
  font-weight: 950;
}

.lesson-main {
  display: grid;
  grid-template-columns: 310px minmax(0, 1fr);
  gap: 24px;
  width: min(1720px, calc(100% - 36px));
  margin: 34px auto;
  align-items: start;
}

.material-nav {
  position: sticky;
  top: 18px;
  /* 🔴 8 个 tab 的菜单总高会超过某些视口。此时 sticky 会卡在 top 不再移动，
     底部第 8 项（Parent Summary）永远露不出来 —— 必须滚到页面底部才看得到，
     用户会误以为"没有家长总结"。
     给一个视口上限 + 内部滚动：菜单自己可以滚，第 8 项随时可达。
     （滚到底后滚轮自然交给页面继续滚，不会把用户锁在菜单里。） */
  max-height: calc(100vh - 36px);
  max-height: calc(100dvh - 36px);
  overflow-y: auto;
  scrollbar-width: thin;
  scrollbar-color: rgba(20, 33, 28, 0.22) transparent;
  display: grid;
  gap: 12px;
  border-radius: 30px;
  background: rgba(255, 255, 251, 0.88);
  padding: 18px;
  box-shadow: 0 18px 55px rgba(20, 33, 28, 0.1);
}

/* 菜单自身滚动时才出现的细滚动条（大屏不超高 → 完全不显示，视觉零变化） */
.material-nav::-webkit-scrollbar {
  width: 8px;
}

.material-nav::-webkit-scrollbar-track {
  background: transparent;
}

.material-nav::-webkit-scrollbar-thumb {
  border-radius: 999px;
  background: rgba(20, 33, 28, 0.22);
}

.material-tab {
  cursor: pointer;
  border: 1px solid var(--line);
  border-radius: 20px;
  background: rgba(255, 250, 240, 0.8);
  color: var(--ink);
  padding: 18px;
  text-align: left;
  font: inherit;
  font-size: 1.02rem;
  font-weight: 950;
}

.material-tab span {
  display: block;
  margin-top: 6px;
  color: var(--muted);
  font-size: 0.88rem;
  font-weight: 850;
}

.material-tab.active {
  border-color: transparent;
  background: #14211c;
  color: white;
}

.material-tab.active span {
  color: rgba(255, 255, 255, 0.7);
}

.material-stage {
  border-radius: 34px;
  background: rgba(255, 255, 251, 0.9);
  padding: clamp(20px, 4vw, 42px);
  box-shadow: 0 18px 55px rgba(20, 33, 28, 0.1);
}

.panel-title {
  margin-bottom: 20px;
}

.lesson-panel {
  display: none;
}

.lesson-panel.active {
  display: block;
}

.document-card {
  border: 1px solid var(--line);
  border-radius: 28px;
  background: #fffffb;
  padding: clamp(22px, 4vw, 44px);
}

.lesson-document h1 {
  margin-bottom: 8px;
  font-size: clamp(2rem, 3vw, 3.1rem);
}

.lesson-document h2 {
  margin-top: 32px;
  color: var(--orange);
  font-size: clamp(1.55rem, 2.1vw, 2.15rem);
}

.lesson-document p {
  color: var(--ink);
  font-size: clamp(1.05rem, 1.45vw, 1.28rem);
  line-height: 1.75;
}

.lesson-subtitle {
  color: var(--muted) !important;
  font-weight: 800;
}

.answer-box {
  width: 100%;
  min-height: 98px;
  margin: 10px 0 22px;
  border: 2px dashed rgba(217, 107, 66, 0.38);
  border-radius: 22px;
  background: rgba(255, 250, 240, 0.7);
  color: var(--ink);
  padding: 18px 20px;
  font: inherit;
  font-size: 1.02rem;
  font-weight: 750;
  line-height: 1.6;
}

.answer-box:focus {
  border-color: var(--orange);
  outline: 3px solid rgba(248, 196, 93, 0.35);
}

.choice-stack {
  display: grid;
  gap: 10px;
  margin: 10px 0 22px;
}

.choice-option {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: rgba(255, 250, 240, 0.72);
  padding: 14px 16px;
  font-weight: 850;
}

.choice-option.correct {
  border-color: rgba(33, 132, 82, 0.45);
  background: rgba(207, 238, 218, 0.7);
}

.submission-bar,
.exam-toolbar,
.audio-actions,
.speed-row,
.voice-row {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
}

.submission-bar {
  margin-top: 18px;
}

.result-box {
  margin: 18px 0;
  border-radius: 22px;
  background: rgba(207, 238, 218, 0.72);
  padding: 18px 20px;
  font-weight: 950;
}

.result-box p,
.answer-explanation {
  margin: 8px 0 0;
  color: #31483e;
  font-weight: 850;
  line-height: 1.6;
}

.answer-comparison {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 14px;
}

.answer-side {
  border: 1px solid rgba(20, 33, 28, 0.1);
  border-radius: 18px;
  background: rgba(255, 255, 251, 0.74);
  padding: 14px 16px;
}

.answer-side strong {
  display: block;
  color: #d46f43;
  font-size: 0.8rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.student-side {
  background: rgba(255, 255, 251, 0.9);
}

.expert-side {
  background: rgba(255, 248, 232, 0.92);
  border-color: rgba(248, 196, 93, 0.42);
}

.answer-explanation {
  border-top: 1px dashed rgba(20, 33, 28, 0.15);
  margin-top: 14px;
  padding-top: 12px;
}

.exam-toolbar {
  position: sticky;
  top: 14px;
  z-index: 5;
  border: 1px solid rgba(248, 196, 93, 0.42);
  border-radius: 28px;
  background: #14211c;
  padding: 16px;
}

.exam-toolbar strong {
  border-radius: 999px;
  background: var(--gold);
  color: var(--ink);
  padding: 14px 20px;
  font-size: 1.2rem;
}

.exam-list {
  display: grid;
  gap: 16px;
  margin-top: 18px;
}

.exam-card {
  border: 1px solid var(--line);
  border-radius: 24px;
  background: #fffffb;
  padding: 22px;
}

.exam-card.exam-correct {
  border-color: rgba(33, 132, 82, 0.55);
  background: linear-gradient(145deg, rgba(207, 238, 218, 0.55), #fffffb);
}

.exam-card.exam-incorrect {
  border-color: rgba(217, 107, 66, 0.55);
  background: linear-gradient(145deg, rgba(255, 241, 207, 0.66), #fffffb);
}

.exam-card h3 {
  margin-bottom: 12px;
  font-size: 1.2rem;
}

.choice-option.wrong {
  border-color: rgba(217, 82, 58, 0.5);
  background: rgba(255, 224, 216, 0.65);
}

.exam-feedback {
  margin-top: 16px;
  border-radius: 20px;
  background: rgba(20, 33, 28, 0.06);
  padding: 16px 18px;
}

.exam-feedback strong,
.exam-feedback p {
  display: block;
}

.exam-feedback p {
  margin: 8px 0 0;
  color: #394e46;
  font-weight: 820;
  line-height: 1.55;
}

.exam-feedback .answer-comparison {
  margin-top: 12px;
}

.breakdown-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 14px;
}

.breakdown-grid span {
  border-radius: 999px;
  background: rgba(255, 255, 251, 0.78);
  padding: 8px 12px;
}

@media (max-width: 720px) {
  .answer-comparison {
    grid-template-columns: minmax(0, 1fr);
  }
}

button:disabled,
input:disabled {
  cursor: not-allowed;
}

.audio-room {
  display: grid;
  grid-template-rows: auto auto minmax(0, 1fr);
  height: clamp(620px, calc(100dvh - 32px), 820px);
  box-sizing: border-box;
  overflow: hidden;
  border-radius: 32px;
  background: #14211c;
  color: white;
  padding: clamp(16px, 3vw, 28px);
}

.voice-button,
.speed-button {
  cursor: pointer;
  border: 1px solid rgba(255, 255, 255, 0.12);
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.1);
  color: white;
  padding: 13px 18px;
  font: inherit;
  font-weight: 950;
}

.voice-button span {
  display: block;
  margin-top: 5px;
  color: rgba(255, 255, 255, 0.68);
  font-size: 0.8rem;
}

.voice-button.active span {
  color: rgba(20, 33, 28, 0.72);
}

.voice-button.active,
.speed-button.active {
  border-color: transparent;
  background: var(--gold);
  color: var(--ink);
}

.sticky-player {
  position: static;
  flex: 0 0 auto;
  z-index: 6;
  display: grid;
  gap: 10px;
  margin: 12px 0;
  border: 1px solid rgba(248, 196, 93, 0.35);
  border-radius: 28px;
  background: rgba(20, 33, 28, 0.96);
  padding: 12px 16px;
}

.sticky-player audio {
  width: 100%;
}

.audio-note {
  flex: 0 0 auto;
  margin: 0 0 10px;
  color: rgba(255, 255, 255, 0.72);
  font-weight: 900;
}

.caption-list {
  display: grid;
  min-height: 0;
  overflow: auto;
  gap: 10px;
  align-content: start;
  box-sizing: border-box;
  padding: 10px 8px 0 0;
  overscroll-behavior: contain;
  scroll-behavior: auto;
}

.caption-list::after {
  content: "";
  display: block;
  height: var(--caption-tail, 0px);
  pointer-events: none;
}

.caption-line {
  cursor: pointer;
  border: 1px solid rgba(255, 255, 255, 0.12);
  border-radius: 22px;
  background: rgba(255, 255, 255, 0.09);
  color: rgba(255, 255, 255, 0.74);
  padding: 18px 20px;
  font-size: clamp(1.1rem, 2vw, 1.45rem);
  font-weight: 950;
  line-height: 1.55;
}

.caption-line.active,
.caption-line[data-current="true"] {
  position: relative;
  z-index: 2;
  border-color: transparent;
  background: var(--gold) !important;
  color: var(--ink) !important;
}

.embed-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.embed-card {
  border: 1px solid var(--line);
  border-radius: 28px;
  background: #fffffb;
  padding: 24px;
}

.embed-card .badge {
  display: inline-flex;
  border-radius: 999px;
  background: #fff1cf;
  color: #8d5c00;
  padding: 8px 12px;
  font-weight: 950;
}

.embed-slot {
  display: grid;
  min-height: 240px;
  place-items: center;
  border: 2px dashed rgba(217, 107, 66, 0.34);
  border-radius: 22px;
  background: rgba(255, 250, 240, 0.74);
  color: var(--muted);
  padding: 20px;
  text-align: center;
  font-weight: 950;
}

.embed-slot.vertical {
  min-height: 420px;
  aspect-ratio: 9 / 16;
  margin: 0 auto;
  width: min(100%, 300px);
}

@media (max-width: 980px) {
  .lesson-hero-grid,
  .lesson-main,
  .embed-grid {
    grid-template-columns: minmax(0, 1fr);
  }

  .material-nav {
    position: static;
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 640px) {
  .lesson-hero,
  .lesson-main {
    width: min(100% - 20px, 720px);
  }

  .material-nav {
    grid-template-columns: minmax(0, 1fr);
  }

  .lesson-hero h1 {
    font-size: clamp(2.15rem, 11vw, 3.4rem);
  }

  .audio-room {
    display: grid;
    grid-template-rows: auto auto minmax(0, 1fr);
    height: clamp(600px, calc(100dvh - 16px), 780px);
    min-height: 0;
    overflow: hidden;
    padding: 16px;
  }

  .voice-row {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .voice-button {
    min-width: 0;
    padding: 10px 4px;
    font-size: 0.78rem;
  }

  .sticky-player {
    gap: 8px;
    margin: 8px 0;
    padding: 9px 10px;
  }

  .speed-row {
    flex-wrap: nowrap;
    align-items: center;
    gap: 5px;
  }

  .speed-button {
    min-width: 0;
    padding: 8px 5px;
    font-size: 0.74rem;
  }

  .speed-row strong {
    flex: 0 0 auto;
    font-size: 0.72rem;
  }

  .speed-button {
    flex: 1 1 0;
  }

  .caption-list {
    min-height: 0;
    max-height: none;
    gap: 8px;
    padding-top: 8px;
  }

  .caption-line {
    padding: 12px 14px;
    line-height: 1.4;
  }
}

/* ==== PVS-TAB-CSS v2 (Parent Summary 家长可见摘要) ==== */
.lesson-document.parent-summary {
  max-width: 78ch;
}
.lesson-document.parent-summary .parent-lead {
  margin: 0 0 4px;
  border: 1px solid var(--line);
  border-radius: 20px;
  background: rgba(255, 250, 240, 0.85);
  padding: 16px 20px;
  color: var(--muted);
  font-size: 1rem;
  font-weight: 800;
  line-height: 1.7;
}
.lesson-document.parent-summary .parent-title {
  margin: 26px 0 6px;
  color: var(--ink);
  font-size: clamp(1.35rem, 1.9vw, 1.86rem);
  font-weight: 900;
  line-height: 1.4;
}
.lesson-document.parent-summary .parent-facts {
  display: grid;
  gap: 10px;
  margin: 18px 0 8px;
}
.lesson-document.parent-summary .parent-facts > div {
  display: grid;
  grid-template-columns: 104px minmax(0, 1fr);
  gap: 12px;
  align-items: baseline;
  border-bottom: 1px dashed var(--line);
  padding-bottom: 10px;
}
.lesson-document.parent-summary .parent-facts dt {
  color: var(--muted);
  font-size: 0.94rem;
  font-weight: 900;
}
.lesson-document.parent-summary .parent-facts dd {
  margin: 0;
  color: var(--ink);
  font-size: 1.02rem;
  font-weight: 800;
  line-height: 1.6;
}
.lesson-document.parent-summary h2 {
  margin-top: 34px;
  margin-bottom: 10px;
  border-left: 6px solid var(--orange);
  padding-left: 14px;
  color: var(--ink);
  font-size: clamp(1.14rem, 1.5vw, 1.36rem);
  font-weight: 900;
  line-height: 1.45;
}
.lesson-document.parent-summary p {
  margin: 0 0 12px;
  font-size: 1.03rem;
  line-height: 1.8;
}
.lesson-document.parent-summary .parent-label {
  margin: 18px 0 6px;
  color: var(--orange);
  font-size: 0.96rem;
  font-weight: 900;
  letter-spacing: 0.04em;
}
.lesson-document.parent-summary ul,
.lesson-document.parent-summary ol {
  display: grid;
  gap: 8px;
  margin: 0 0 12px;
  padding-left: 24px;
}
.lesson-document.parent-summary li {
  color: var(--ink);
  font-size: 1.03rem;
  line-height: 1.75;
}
@media (max-width: 720px) {
  .lesson-document.parent-summary .parent-facts > div {
    grid-template-columns: minmax(0, 1fr);
    gap: 2px;
  }
}

/* ==== I18N-BILINGUAL v1 (菜单与标题的中英对照小字) ==== */
/* 规则：中文为主（原有字号），英文为辅（下方小字）。
   字号用 rem 固定，保证在任何父元素下都清晰可读。 */
.i18n-en {
  display: block;
  margin-top: 6px;
  color: var(--muted);
  font-size: 0.88rem;
  font-weight: 850;
  letter-spacing: 0.01em;
  line-height: 1.42;
  text-transform: none;
}
.lesson-hero h1 .i18n-en {
  margin-top: 12px;
  font-size: clamp(0.98rem, 1.15vw, 1.28rem);
  font-weight: 800;
  letter-spacing: 0.02em;
  color: rgba(20, 33, 28, 0.68);
}
.hero-lead .i18n-en {
  margin-top: 8px;
  font-size: 0.92rem;
  font-weight: 700;
  line-height: 1.6;
  color: rgba(20, 33, 28, 0.62);
}
.lesson-progress-card h2 .i18n-en,
.panel-title h2 .i18n-en {
  margin-top: 5px;
}
.nav-links a .i18n-en {
  margin-top: 3px;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: #5d6f66;
}
.home-pill .i18n-en,
.member-pill .i18n-en {
  margin-top: 2px;
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: inherit;
  opacity: 0.82;
}
/* 按钮内的小字跟随按钮前景色，深浅底都看得清 */
button .i18n-en,
.primary-action .i18n-en,
.secondary-action .i18n-en,
.embed-card .i18n-en {
  margin-top: 4px;
  font-size: 0.74rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: inherit;
  opacity: 0.78;
}
.embed-card h3 .i18n-en {
  font-size: 0.8rem;
  opacity: 0.72;
}
.site-footer .i18n-en {
  margin-top: 6px;
  font-size: 0.8rem;
  font-weight: 700;
}
/* ==== /I18N-BILINGUAL ==== */

/* ==== 手机端横向溢出防护（2026-09-16）====
   与首页同一口径：网格列 `1fr` 的最小值是 min-content，内部不可收缩的
   元素会把整列顶得比屏幕宽（手机上看就是右侧被切掉）。 */
.lesson-hero-grid > *,
.lesson-main > *,
.embed-grid > *,
.material-nav > *,
.material-tab,
.material-stage,
.lesson-panel,
.document-card {
  min-width: 0;
}

.lesson-hero,
.lesson-main,
.material-nav,
.material-stage,
.lesson-panel,
.document-card {
  overflow-wrap: anywhere;
}

/* 控件不得超出容器（安卓上 <input> 默认宽度会随字体回退变大） */
.lesson-main input,
.lesson-main select,
.lesson-main textarea,
.lesson-hero input {
  max-width: 100%;
  min-width: 0;
}

@media (max-width: 640px) {
  .material-tab {
    padding: 14px 16px;
  }

  .choice-option {
    overflow-wrap: anywhere;
  }
}
/* ==== 教师友好版式 · 课号徽章 / 答案对照 / 本课深度讲解（2026-09-16）====
   追加块。原有规则一律不动，只在这里覆盖需要改的部分。
   三件事：
     ① 课号放大成徽章 —— 学生/家长一眼看到「这是第几课」
     ② 答案对照分色 —— 题面(要问什么) / 参考答案 / 教师讲解 / 中文讲解 / 要点 / 脚手架
     ③ 本课深度讲解面板的版式（语言切换 + 双语双音轨）
   ==========================================================================*/

/* ---------- ① 课号徽章 ---------- */
.lesson-hero-grid .eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  margin: 0 0 16px;
  padding: 5px;
  border: 1px solid rgba(233, 127, 0, 0.3);
  border-radius: 999px;
  background: rgba(233, 127, 0, 0.1);
  font-size: 1rem;
  letter-spacing: 0;
  line-height: 1.2;
  text-transform: none;
}

.lesson-hero-grid .eyebrow .eyebrow-no {
  display: inline-grid;
  min-width: 88px;
  padding: 9px 17px;
  place-items: center;
  border-radius: 999px;
  background: var(--orange);
  color: #fff;
  font-size: clamp(1rem, 1.5vw, 1.22rem);
  font-weight: 950;
  letter-spacing: 0.03em;
  white-space: nowrap;
  box-shadow: 0 8px 18px rgba(233, 127, 0, 0.32);
}

.lesson-hero-grid .eyebrow .eyebrow-sub {
  padding-right: 17px;
  color: #a4581c;
  font-size: clamp(0.86rem, 1.15vw, 1.02rem);
  font-weight: 850;
  letter-spacing: 0.04em;
  white-space: nowrap;
}

@media (max-width: 560px) {
  .lesson-hero-grid .eyebrow {
    gap: 8px;
    padding: 4px;
  }

  .lesson-hero-grid .eyebrow .eyebrow-no {
    min-width: 0;
    padding: 8px 13px;
  }

  .lesson-hero-grid .eyebrow .eyebrow-sub {
    padding-right: 12px;
    font-size: 0.8rem;
  }
}

/* ---------- ② 答案对照 · 教师友好配色 ----------
   取材自课堂实况：老师要「念题 → 看答案 → 追问」，
   所以题面必须是最大的深色字，答案必须自带色块和标签，
   两者绝不能用同一个颜色。整体暖白纸底 + 深墨绿字（不用纯黑纯白）护眼。 */
#answerDocument .ak-doc {
  color: #1b2a24;
}

#answerDocument .ak-sec {
  margin: 0 0 26px;
  padding: 0;
}

#answerDocument .ak-h {
  margin: 30px 0 14px;
  padding-left: 14px;
  border-left: 6px solid var(--orange);
  color: #16241e;
  font-size: clamp(1.28rem, 1.9vw, 1.7rem);
  font-weight: 950;
  line-height: 1.35;
}

#answerDocument .ak-sec > p,
#answerDocument .ak-doc > p {
  max-width: 74ch;
  margin: 0 0 12px;
  color: #24352d;
  font-size: clamp(1.02rem, 1.34vw, 1.15rem);
  font-weight: 650;
  line-height: 1.85;
}

/* 编号问答题对：题面一条、答案一条，颜色与底色都不同 */
#answerDocument .ak-qa {
  margin: 0 0 16px;
  border: 1px solid rgba(20, 33, 28, 0.12);
  border-radius: 18px;
  background: #fffefb;
  overflow: hidden;
}

#answerDocument .ak-ques {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  margin: 0;
  padding: 14px 18px;
  border-bottom: 1px solid rgba(20, 33, 28, 0.1);
  background: rgba(20, 33, 28, 0.055);
  color: #14211c;
  font-size: clamp(1.06rem, 1.42vw, 1.22rem);
  font-weight: 900;
  line-height: 1.6;
}

#answerDocument .ak-no {
  display: inline-grid;
  flex: 0 0 auto;
  min-width: 36px;
  height: 36px;
  padding: 0 9px;
  place-items: center;
  border-radius: 11px;
  background: #14211c;
  color: var(--gold);
  font-size: 1rem;
  font-weight: 950;
  line-height: 1;
}

#answerDocument .ak-ques-text {
  min-width: 0;
}

#answerDocument .ak-ans {
  margin: 0;
  padding: 14px 18px 16px;
  border-left: 7px solid #12866a;
  background: linear-gradient(180deg, rgba(18, 134, 106, 0.12), rgba(18, 134, 106, 0.04));
  color: #0e3227;
  font-size: clamp(1.03rem, 1.36vw, 1.18rem);
  font-weight: 720;
  line-height: 1.8;
}

#answerDocument .ak-tag {
  display: inline-block;
  margin: 0 0 8px;
  padding: 4px 11px;
  border-radius: 999px;
  background: #12866a;
  color: #fff;
  font-size: 0.72rem;
  font-weight: 900;
  letter-spacing: 0.07em;
  text-transform: uppercase;
}

#answerDocument .ak-ans-text {
  display: block;
}

/* 标签行：左标签右内容，扫读时一眼定位 */
#answerDocument .ak-row {
  display: grid;
  grid-template-columns: minmax(0, 190px) minmax(0, 1fr);
  gap: 6px 14px;
  align-items: start;
  margin: 0 0 10px;
  padding: 11px 14px;
  border-left: 5px solid var(--ak-accent, rgba(20, 33, 28, 0.25));
  border-radius: 12px;
  background: rgba(20, 33, 28, 0.035);
}

#answerDocument .ak-key {
  display: inline-block;
  padding: 4px 10px;
  border-radius: 8px;
  background: var(--ak-accent, #556e64);
  color: #fff;
  font-size: 0.76rem;
  font-weight: 900;
  letter-spacing: 0.03em;
  line-height: 1.4;
  overflow-wrap: anywhere;
}

#answerDocument .ak-val {
  min-width: 0;
  color: #1b2a24;
  font-size: clamp(1rem, 1.3vw, 1.13rem);
  font-weight: 620;
  line-height: 1.8;
  overflow-wrap: anywhere;
}

/* 六类语义色：题面 / 参考答案 / 教师讲解 / 中文讲解 / 核心要点 / 脚手架 */
#answerDocument .ak-c-q {
  --ak-accent: #24352d;
  background: rgba(20, 33, 28, 0.07);
}

#answerDocument .ak-c-a {
  --ak-accent: #12866a;
  background: rgba(18, 134, 106, 0.11);
}

#answerDocument .ak-c-tip {
  --ak-accent: #3b52c4;
  background: rgba(59, 82, 196, 0.08);
}

#answerDocument .ak-c-zh {
  --ak-accent: #b0691a;
  background: rgba(176, 105, 26, 0.11);
}

#answerDocument .ak-c-key {
  --ak-accent: #4d6b5f;
  background: rgba(77, 107, 95, 0.09);
}

#answerDocument .ak-c-ev {
  --ak-accent: #8a4f9e;
  background: rgba(138, 79, 158, 0.085);
}

#answerDocument .ak-c-txt {
  --ak-accent: #6a5b46;
  background: rgba(106, 91, 70, 0.08);
}

#answerDocument .ak-c-opt {
  --ak-accent: #12866a;
  background: rgba(18, 134, 106, 0.06);
}

/* 题面类的值也加粗 —— 老师照着念的就是它 */
#answerDocument .ak-c-q .ak-val {
  color: #14211c;
  font-weight: 870;
}

/* 中文讲解：中文友好的行距，给中文家长/学生看 */
#answerDocument .ak-c-zh .ak-val {
  font-weight: 700;
  line-height: 1.9;
}

@media (max-width: 640px) {
  #answerDocument .ak-row {
    grid-template-columns: minmax(0, 1fr);
    gap: 6px;
  }

  #answerDocument .ak-qa {
    border-radius: 15px;
  }

  #answerDocument .ak-ques {
    padding: 12px 14px;
  }

  #answerDocument .ak-ans {
    padding: 12px 14px 14px;
  }
}

/* ---------- ③ 本课深度讲解 ---------- */
.dd-switch {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 0 0 14px;
}

.dd-lang {
  display: inline-flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 2px;
  border: 1px solid rgba(20, 33, 28, 0.14);
  border-radius: 16px;
  background: #fffdf7;
  color: var(--ink);
  padding: 10px 18px;
  font: inherit;
  font-size: 1rem;
  font-weight: 900;
  cursor: pointer;
}

.dd-lang span {
  color: var(--muted);
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.04em;
}

.dd-lang.active {
  border-color: var(--ink);
  background: var(--ink);
  color: #fff;
}

.dd-lang.active span {
  color: var(--gold);
}

.dd-audio {
  display: grid;
  gap: 10px;
  margin: 0 0 16px;
}

.dd-track {
  display: grid;
  gap: 8px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: #fffdf7;
  padding: 13px 16px;
}

.dd-track-head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 10px;
  min-width: 0;
}

.dd-track-head strong {
  color: var(--ink);
  font-size: 1rem;
  font-weight: 900;
}

.dd-track-head span {
  color: var(--muted);
  font-size: 0.76rem;
  font-weight: 800;
  letter-spacing: 0.03em;
}

.dd-track audio {
  width: 100%;
  min-width: 0;
  max-width: 100%;
}

.dd-doc .lesson-document h2 {
  margin-top: 26px;
}

.dd-doc .lesson-document p {
  max-width: 76ch;
  font-size: clamp(1.06rem, 1.4vw, 1.22rem);
  line-height: 1.92;
}

.dd-doc .dd-lead {
  color: #14211c !important;
  font-size: clamp(1.12rem, 1.55vw, 1.34rem) !important;
  font-weight: 850;
}

.dd-doc .dd-story {
  border-left: 6px solid var(--gold);
  background: rgba(248, 196, 93, 0.14);
  border-radius: 0 16px 16px 0;
  padding: 16px 20px;
  margin: 0 0 18px;
}

.dd-lang-block[hidden] {
  display: none !important;
}

.dd-note {
  margin: 18px 0 0;
  border-radius: 16px;
  background: rgba(20, 33, 28, 0.05);
  padding: 14px 18px;
  color: #24352d;
  font-size: 0.98rem;
  font-weight: 650;
  line-height: 1.75;
}
/* ==== 教师友好版式 · 结束 ==== */