:root {
  color-scheme: light;
  --font-display: "Nunito", "SF Pro Display", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-body: "Inter", "SF Pro Text", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --bg: #FAFCFB; /* 非常非常浅的背景，几乎接近白 */
  --surface: #FFFFFF;
  --surface-alt: #F0F6F4; /* 淡淡的豆绿作为辅助背景（比如 header） */
  --text-main: #111827; /* 近黑，增强对比 */
  --text: #111827; /* 保持兼容 */
  --muted: #6B7280; /* 更轻的辅助灰 */
  --brand: #1E3A8A; /* 藏青色主品牌色，去除绿色 */
  --brand-dark: #1E40AF;
  --brand-rgb: 30 58 138;
  --accent: #E76F51;
  --border: #E5E5EA; /* 中性淡灰边框 */
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 18px 36px rgba(0, 0, 0, 0.08);
  --shadow-button: 0 4px 12px rgb(var(--brand-rgb) / 0.3);
  --shadow-button-hover: 0 6px 16px rgb(var(--brand-rgb) / 0.4);
  --shadow: 0 18px 36px rgba(0, 0, 0, 0.08);
  --shadow-soft: 0 10px 24px rgba(0, 0, 0, 0.04);
  --radius-lg: 22px;
  --radius-md: 16px;
  --radius-sm: 12px;
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-7: 32px;
  --space-8: 40px;
  --space-9: 56px;
  --transition-fast: 0.16s ease;
  --transition-medium: 0.28s ease;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  line-height: 1.6;
  min-height: 100vh;
}

a {
  color: inherit;
  text-decoration: none;
}

h1,
h2,
h3,
h4 {
  font-family: var(--font-display);
  font-weight: 700;
  letter-spacing: 0.02em;
}

.page {
  max-width: 1200px;
  margin: var(--space-7) auto var(--space-9);
  padding: 0 var(--space-6);
}

.app-header {
  background: var(--surface-alt);
  color: var(--text);
  padding: var(--space-8) 0;
  border-bottom: 1px solid var(--border);
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.02); /* 精细隔离层阴影 */
}

.app-header--compact {
  padding: var(--space-7) 0;
}

.app-header__content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-6);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-6);
  flex-wrap: wrap;
}

.app-header__intro {
  max-width: 560px;
}

.app-header__eyebrow {
  font-weight: 600;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  opacity: 0.85;
  margin-bottom: var(--space-2);
  font-size: 12px;
}

.app-header__title {
  font-family: var(--font-display);
  font-weight: 700;
  letter-spacing: 0.02em;
  font-size: clamp(28px, 4vw, 40px);
}

.app-header__subtitle {
  margin-top: var(--space-3);
  opacity: 0.92;
  font-size: 15px;
}

.app-header__actions {
  display: flex;
  gap: var(--space-2);
  margin-top: var(--space-4);
  flex-wrap: wrap;
}

.app-header__stats {
  display: flex;
  gap: var(--space-3);
  flex-wrap: wrap;
}

.stat-card {
  background: var(--surface);
  border: none;
  border-radius: var(--radius-md);
  padding: var(--space-4) var(--space-5);
  min-width: 150px;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition-medium), box-shadow var(--transition-medium);
}

.stat-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}

.stat-card__value {
  font-size: 26px;
  font-weight: 700;
  font-family: var(--font-display);
}

.stat-card__label {
  opacity: 0.85;
  margin-top: var(--space-1);
  font-size: 13px;
}

.section-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-end;
  gap: var(--space-4);
  margin-bottom: var(--space-6);
  flex-wrap: wrap;
}

.section-header__title h2 {
  font-family: var(--font-display);
  font-size: 24px;
}

.section-header__meta {
  display: flex;
  gap: var(--space-2);
  flex-wrap: wrap;
}

.section-header p {
  color: var(--muted);
  max-width: 520px;
}

.pill {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 6px 12px;
  border-radius: 999px;
  background: transparent;
  color: inherit;
  font-size: 12px;
  font-weight: 700;
  border: 1px solid transparent;
}

.pill--outline {
  background: transparent;
  border-color: var(--brand);
  color: var(--brand-dark);
}

.pill--light {
  background: var(--surface);
  color: var(--brand-dark);
  border: 1px solid var(--brand);
}

.section-header .pill {
  background: var(--surface);
  color: var(--brand-dark);
  border: 1px solid var(--brand);
  box-shadow: 0 2px 6px rgb(var(--brand-rgb) / 0.1);
}

.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: var(--space-5);
}

.video-card {
  background: var(--surface);
  border-radius: var(--radius-lg);
  border: none;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: transform var(--transition-medium), box-shadow var(--transition-medium);
  box-shadow: var(--shadow-sm);
}

.video-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-lg);
}

.video-card__cover {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
  display: block;
}

.video-card__body {
  padding: var(--space-5) var(--space-5) var(--space-6);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.video-card__title {
  font-size: 16px;
  font-weight: 600;
}

.video-card__meta {
  color: var(--muted);
  font-size: 13px;
}

.video-card__tags {
  display: flex;
  gap: var(--space-2);
  flex-wrap: wrap;
}

.tag {
  background: transparent;
  color: inherit;
  padding: 4px 10px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
  border: 1px solid transparent;
}

/* Tag & Pill Color Modifiers */
.pill--brand, .tag--brand {
  background: rgb(var(--brand-rgb) / 0.1);
  color: var(--brand-dark);
  border-color: rgb(var(--brand-rgb) / 0.3);
}

.pill--neutral, .tag--neutral {
  background: rgba(107, 114, 128, 0.1);
  color: var(--muted);
  border-color: rgba(107, 114, 128, 0.3);
}

.primary-button {
  margin-top: var(--space-3);
  padding: 10px 16px;
  border-radius: var(--radius-sm);
  background: linear-gradient(180deg, var(--brand) 0%, var(--brand-dark) 100%);
  color: #ffffff;
  border: none;
  text-align: center;
  font-weight: 600;
  cursor: pointer;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), filter var(--transition-fast);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.25), var(--shadow-button);
}

.primary-button:hover {
  transform: translateY(-1px);
  filter: brightness(1.05);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.35), var(--shadow-button-hover);
}

.primary-button:active {
  transform: translateY(2px);
  filter: brightness(0.95);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.1), 0 2px 4px rgb(var(--brand-rgb) / 0.4);
}

.ghost-button {
  border: 1px solid var(--border);
  background: var(--surface);
  padding: 10px 16px;
  border-radius: var(--radius-sm);
  color: var(--text);
  font-weight: 600;
  transition: transform var(--transition-fast), background var(--transition-fast), border-color var(--transition-fast);
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.02);
}

.ghost-button:hover {
  transform: translateY(-1px);
  background: #F2F2F7;
  border-color: #D1D1D6;
}

.panel {
  background: var(--surface);
  border-radius: var(--radius-lg);
  border: none;
  box-shadow: var(--shadow-md);
  transition: transform var(--transition-medium), box-shadow var(--transition-medium);
}

.panel:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.player-layout {
  display: grid;
  grid-template-columns: minmax(0, 2.1fr) minmax(0, 1fr);
  gap: var(--space-6);
  align-items: start;
}

.player-stage {
  display: grid;
  gap: var(--space-6);
}

.player-shadowing {
  display: grid;
  gap: var(--space-5);
  padding: var(--space-5);
}

.player-video {
  padding: var(--space-4);
  min-height: 360px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.player-video iframe {
  width: 100%;
  min-height: 360px;
  border-radius: var(--radius-md);
  border: none;
}

.player-meta {
  display: grid;
  gap: var(--space-5);
}

.player-meta__card {
  background: var(--surface);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  padding: var(--space-5);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  box-shadow: var(--shadow-soft);
}

.player-meta__card h3 {
  font-size: 16px;
  font-family: var(--font-display);
}

.player-meta__desc {
  color: var(--muted);
  font-size: 14px;
  line-height: 1.6;
}

.step-list {
  display: grid;
  gap: var(--space-2);
  padding-left: 18px;
  color: var(--muted);
  font-size: 14px;
}

.player-meta__tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.player-meta__row {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  color: var(--muted);
  font-size: 14px;
}

.player-meta__row span {
  color: var(--text);
  font-weight: 600;
}

.shadowing-progress {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  font-size: 12px;
  color: var(--muted);
}

.subtitle-line {
  line-height: 1.6;
}

.subtitle-line--en {
  font-size: 16px;
  font-weight: 600;
  color: var(--text);
}

.subtitle-line--zh {
  font-size: 14px;
  color: var(--muted);
}

.phrase-annotation-panel {
  margin-top: var(--space-3);
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 10px 12px;
  display: grid;
  gap: var(--space-2);
}

.phrase-annotation-panel__header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-2);
  flex-wrap: wrap;
}

.phrase-annotation-panel__title {
  font-size: 12px;
  font-weight: 700;
  color: var(--text);
}

.phrase-annotation-panel__meta {
  font-size: 12px;
  color: var(--muted);
}

.phrase-annotation-list {
  list-style: none;
  display: grid;
  gap: var(--space-2);
}

.phrase-annotation-item {
  display: grid;
  gap: 4px;
  padding: 8px 10px;
  border-radius: 10px;
  background: var(--surface-alt);
  border: 1px solid var(--border);
}

.phrase-annotation-item__text {
  font-weight: 700;
  font-size: 13px;
  color: var(--brand);
}

.phrase-annotation-item__explanation {
  font-size: 12px;
  line-height: 1.5;
  color: var(--muted);
}

.phrase-annotation-item__explanation--empty {
  opacity: 0.8;
}

.phrase-annotation-empty {
  font-size: 12px;
  color: var(--muted);
}

.phrase-highlight {
  background: #fdf2ef;
  color: #c64d30;
  border: 1px solid #fad4ca;
  border-radius: 999px;
  padding: 2px 6px;
  font-weight: 600;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 4px;
  margin: 0 2px;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.phrase-highlight.is-collected {
  background: rgb(var(--brand-rgb) / 0.16);
  color: var(--brand-dark);
  border-color: rgb(var(--brand-rgb) / 0.3);
}

.control-button,
.danger-button,
.ghost-button--solid {
  border-radius: var(--radius-sm);
  padding: 8px 14px;
  font-weight: 600;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text-main);
  cursor: pointer;
  transition: transform var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast), background var(--transition-fast), color var(--transition-fast);
}

.control-button:hover,
.ghost-button--solid:hover {
  transform: translateY(-1px);
  border-color: var(--brand);
  color: var(--brand);
  box-shadow: var(--shadow-sm);
}

.danger-button {
  background: var(--brand);
  border-color: var(--brand);
  color: #ffffff;
  box-shadow: var(--shadow-button);
}

.danger-button:hover {
  transform: translateY(-1px);
  background: var(--brand-dark);
  box-shadow: var(--shadow-button-hover);
}

.control-button:disabled,
.danger-button:disabled,
.ghost-button--solid:disabled,
.sentence-row__action:disabled {
  cursor: not-allowed;
  opacity: 0.5;
  transform: none;
  box-shadow: none;
}

.file-input-hidden {
  display: none;
}

.shadowing-record__audio {
  width: 100%;
}

.score-pill {
  background: rgb(var(--brand-rgb) / 0.15);
  color: var(--brand-dark);
  padding: 2px 8px;
  border-radius: 999px;
  font-weight: 600;
  font-size: 12px;
}

.sentence-list {
  list-style: none;
  display: grid;
  gap: var(--space-3);
}

.sentence-row {
  display: grid;
  grid-template-columns: 132px minmax(0, 1fr);
  align-items: center;
  gap: var(--space-3);
}

.sentence-row__action {
  width: 100%;
  min-height: 44px;
  margin-top: 0;
  align-self: center;
}

.sentence-item {
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 10px 12px;
  display: grid;
  gap: 6px;
  background: var(--surface);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast), transform var(--transition-fast);
}

.sentence-item--current {
  border-color: var(--brand);
  background: var(--surface-alt);
  padding: 14px;
  gap: var(--space-3);
}

.sentence-item--context {
  background: var(--surface);
}

.current-sentence-actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex-wrap: wrap;
}

.current-score {
  display: inline-flex;
  align-items: baseline;
  gap: 6px;
  padding: 7px 10px;
  border-radius: var(--radius-sm);
  background: rgb(var(--brand-rgb) / 0.15);
  color: var(--brand-dark);
  font-size: 12px;
  font-weight: 600;
}

.current-score strong {
  font-size: 16px;
}

.sentence-item__button {
  border: none;
  background: transparent;
  text-align: left;
  font-size: 14px;
  font-weight: 600;
  display: grid;
  gap: 6px;
  line-height: 1.5;
  cursor: pointer;
  color: var(--text);
}

.sentence-item__en {
  font-size: 14px;
  font-weight: 600;
  color: var(--text);
}

.sentence-item__zh {
  font-size: 12px;
  font-weight: 500;
  color: var(--muted);
}

.sentence-item__meta {
  display: flex;
  justify-content: space-between;
  gap: 8px;
  font-size: 12px;
  color: var(--muted);
}

.phrase-panel {
  display: grid;
  gap: var(--space-2);
}

.phrase-panel__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
}

.phrase-panel__header h4 {
  font-size: 14px;
}

.phrase-count {
  font-size: 12px;
  font-weight: 600;
  color: var(--muted);
}

.phrase-list {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.phrase-pill {
  background: rgb(var(--brand-rgb) / 0.12);
  border: 1px solid rgb(var(--brand-rgb) / 0.2);
  color: var(--brand-dark);
  border-radius: 999px;
  padding: 6px 10px;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: transform var(--transition-fast), border-color var(--transition-fast);
}

.phrase-pill__icon {
  font-weight: 700;
}

.phrase-empty {
  font-size: 12px;
  color: var(--muted);
}

.shadowing-tip {
  font-size: 12px;
  color: var(--muted);
}

.empty-state {
  text-align: center;
  color: var(--muted);
}

@media (max-width: 900px) {
  .player-layout {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 640px) {
  .sentence-row {
    grid-template-columns: minmax(0, 1fr);
    gap: var(--space-2);
  }

  .sentence-row__action {
    width: auto;
    justify-self: start;
  }
}