.page-topics {
  --tp-rail: 208px;
  padding-bottom: var(--section-y-lg);
}

/* ---------- 面包屑 ---------- */
.page-topics .breadcrumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1);
  margin-bottom: var(--space-6);
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}
.page-topics .breadcrumb a {
  color: var(--color-primary);
  text-decoration: none;
}
.page-topics .breadcrumb a:hover {
  text-decoration: underline;
  text-underline-offset: 3px;
}
.page-topics .breadcrumb [aria-current="page"] {
  color: var(--color-ink);
}

/* ---------- 首屏 ---------- */
.page-topics .topics-hero {
  padding: var(--space-6) 0 var(--section-y);
}

.page-topics .hero-grid {
  display: grid;
  gap: var(--space-6);
}

@media (min-width: 1024px) {
  .page-topics .hero-grid {
    grid-template-columns: minmax(0, 4.5fr) minmax(0, 5fr) minmax(0, 2.5fr);
    align-items: start;
    gap: var(--space-6);
  }
}

.page-topics .hero-kicker {
  margin: 0 0 var(--space-2);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}

.page-topics .display-title {
  margin: 0 0 var(--space-3);
  font-size: var(--text-display);
  line-height: var(--leading-heading);
  font-weight: var(--weight-heading);
  color: var(--color-ink);
}

.page-topics .lead {
  margin: 0;
  max-width: 42ch;
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
}

.page-topics .hero-stats {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
  margin: var(--space-6) 0 0;
  padding: 0;
}

.page-topics .hero-stats .stat {
  display: flex;
  flex-direction: column;
  gap: 2px;
  padding-left: var(--space-2);
  border-left: 3px solid var(--color-primary);
}

.page-topics .stat-key {
  margin: 0;
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}

.page-topics .stat-num {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--text-figure);
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--color-accent);
}

/* 4×4 编号网格 */
.page-topics .num-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin: 0;
  padding: 0;
  list-style: none;
}

@media (min-width: 560px) {
  .page-topics .num-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

.page-topics .num-grid li {
  border-top: var(--border-thin) solid var(--color-line);
}

.page-topics .num-grid a {
  display: block;
  padding: var(--space-2) var(--space-1) var(--space-2) 0;
  text-decoration: none;
  transition: background-color 140ms ease-out;
}

.page-topics .num-grid a:hover {
  background-color: var(--color-primary-soft);
}

.page-topics .num-code {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-3xl);
  line-height: 1.05;
  letter-spacing: -0.03em;
  color: var(--color-primary);
}

.page-topics .num-grid li:nth-child(odd) .num-code {
  margin-left: -0.06em;
}

.page-topics .num-name {
  display: block;
  margin-top: 2px;
  font-size: var(--text-sm);
  color: var(--color-ink-muted);
}

/* 首屏图片 */
.page-topics .hero-figure {
  position: relative;
  margin: 0;
  border-radius: var(--radius-sm);
  overflow: hidden;
}

.page-topics .hero-figure img {
  display: block;
  width: 100%;
  aspect-ratio: 4 / 3;
  object-fit: cover;
  filter: saturate(0.55);
}

.page-topics .hero-figure::after {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--color-primary);
  mix-blend-mode: multiply;
  opacity: 0.18;
  pointer-events: none;
}

.page-topics .hero-figure .figure-caption {
  position: relative;
  z-index: 1;
  margin: 0;
  padding: var(--space-1) 0 0;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}

@media (min-width: 1024px) {
  .page-topics .hero-figure img {
    aspect-ratio: 3 / 4;
  }
}

/* ---------- 六类方向标签带 ---------- */
.page-topics .band-list {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 0;
  margin: var(--space-6) 0 0;
  padding: 0;
  list-style: none;
}

@media (min-width: 640px) {
  .page-topics .band-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (min-width: 1024px) {
  .page-topics .band-list {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

.page-topics .band {
  display: grid;
  grid-template-columns: 3px minmax(0, 1fr);
  grid-template-rows: auto auto;
  column-gap: var(--space-2);
  row-gap: 2px;
  padding: var(--space-3) var(--space-2) var(--space-3) 0;
  border-bottom: var(--border-thin) solid var(--color-line);
}

.page-topics .band-bar {
  grid-row: 1 / span 2;
  width: 3px;
  align-self: stretch;
  background: var(--color-primary);
  transition: background-color 140ms ease-out;
}

.page-topics .band:hover .band-bar {
  background: var(--color-accent);
}

.page-topics .band-name {
  font-size: var(--text-lg);
  line-height: 1.3;
  color: var(--color-ink);
}

.page-topics .band-count {
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}

/* ---------- 目录区 ---------- */
.page-topics .catalog-layout {
  display: grid;
  gap: var(--space-6);
  margin-top: var(--space-6);
}

@media (min-width: 1024px) {
  .page-topics .catalog-layout {
    grid-template-columns: var(--tp-rail) minmax(0, 1fr);
    gap: var(--space-8);
    align-items: start;
  }
}

/* 方向索引 */
.page-topics .dir-rail-title {
  margin: 0 0 var(--space-2);
  padding-bottom: var(--space-1);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  color: var(--color-ink-muted);
  border-bottom: var(--border-thin) solid var(--color-line);
}

.page-topics .dir-rail-list {
  display: flex;
  gap: var(--space-1);
  overflow-x: auto;
  margin: 0;
  padding: 0 0 var(--space-1);
  list-style: none;
  -webkit-overflow-scrolling: touch;
}

.page-topics .dir-rail-list li {
  flex: 0 0 auto;
}

.page-topics .dir-rail-list a {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--space-2);
  padding: var(--space-1) var(--space-2);
  border-left: 3px solid transparent;
  font-size: var(--text-sm);
  color: var(--color-ink);
  text-decoration: none;
  white-space: nowrap;
  transition: border-color 140ms ease-out, background-color 140ms ease-out;
}

.page-topics .dir-rail-list a:hover,
.page-topics .dir-rail-list a:focus-visible {
  border-left-color: var(--color-primary);
  background-color: var(--color-primary-soft);
}

.page-topics .dir-rail-count {
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}

@media (min-width: 1024px) {
  .page-topics .dir-rail {
    position: sticky;
    top: var(--space-3);
  }

  .page-topics .dir-rail-list {
    display: block;
    overflow: visible;
    padding-bottom: 0;
  }

  .page-topics .dir-rail-list li + li {
    margin-top: 2px;
  }

  .page-topics .dir-rail-list a {
    padding: var(--space-1) var(--space-2);
  }
}

/* 方向分组 */
.page-topics .dir-group + .dir-group {
  margin-top: var(--space-8);
}

.page-topics .dir-group-head {
  display: grid;
  gap: var(--space-3);
  padding-bottom: var(--space-3);
  border-bottom: var(--border-thin) solid var(--color-line);
}

@media (min-width: 768px) {
  .page-topics .dir-group-head--media {
    grid-template-columns: minmax(0, 1fr) 220px;
    align-items: start;
  }
}

.page-topics .dir-group-title {
  margin: 0 0 var(--space-1);
  font-size: var(--text-xl);
  line-height: var(--leading-heading);
  font-weight: var(--weight-heading);
  color: var(--color-ink);
}

.page-topics .dir-group-range {
  margin: 0 0 var(--space-2);
  font-size: var(--text-sm);
  letter-spacing: 0.02em;
  color: var(--color-primary);
}

.page-topics .dir-group-desc {
  margin: 0;
  max-width: var(--measure);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
}

.page-topics .dir-group-figure {
  margin: 0;
  border-radius: var(--radius-sm);
  overflow: hidden;
}

.page-topics .dir-group-figure img {
  display: block;
  width: 100%;
  aspect-ratio: 3 / 2;
  object-fit: cover;
  filter: saturate(0.55);
}

/* 条目索引条 */
.page-topics .entry-list {
  margin: 0;
  padding: 0;
  list-style: none;
}

.page-topics .entry {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: var(--space-1) var(--space-2);
  align-items: baseline;
  padding: var(--space-3) var(--space-1);
  border-bottom: var(--border-thin) solid var(--color-line);
  transition: background-color 140ms ease-out;
}

.page-topics .entry:hover {
  background-color: var(--color-surface-alt);
}

.page-topics .entry-code {
  grid-column: 1;
  grid-row: 1;
  font-family: var(--font-mono);
  font-size: var(--text-lg);
  letter-spacing: -0.01em;
  color: var(--color-primary);
}

.page-topics .entry-state {
  grid-column: 2;
  grid-row: 1;
  justify-self: end;
}

.page-topics .entry-title {
  grid-column: 1 / -1;
  grid-row: 2;
  margin: 0;
  font-size: var(--text-lg);
  line-height: 1.3;
  font-weight: var(--weight-heading);
  color: var(--color-ink);
}

.page-topics .entry-desc {
  grid-column: 1 / -1;
  grid-row: 3;
  margin: 0;
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--color-ink-soft);
}

.page-topics .entry .tag {
  grid-column: 1;
  grid-row: 4;
  justify-self: start;
}

.page-topics .entry-cat {
  grid-column: 2;
  grid-row: 4;
  justify-self: end;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-ink-muted);
}

.page-topics .entry-state {
  display: inline-block;
  padding: 2px 8px;
  border-radius: var(--radius-sm);
  font-size: var(--text-xs);
  line-height: 1.7;
  white-space: nowrap;
}

.page-topics .entry-state--archived {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

.page-topics .entry-state--active {
  background: var(--color-accent);
  color: var(--color-accent-ink);
}

@media (min-width: 1024px) {
  .page-topics .entry {
    grid-template-columns: 60px minmax(0, 1fr) 96px minmax(0, 1.7fr) 74px 88px;
    align-items: center;
    gap: var(--space-2);
    padding: var(--space-2);
  }

  .page-topics .entry-code,
  .page-topics .entry-title,
  .page-topics .entry-desc,
  .page-topics .entry-cat,
  .page-topics .entry-state,
  .page-topics .entry .tag {
    grid-row: 1;
    justify-self: start;
  }

  .page-topics .entry-code { grid-column: 1; }
  .page-topics .entry-title {
    grid-column: 2;
    font-size: var(--text-lg);
  }
  .page-topics .entry .tag { grid-column: 3; }
  .page-topics .entry-desc { grid-column: 4; }
  .page-topics .entry-cat { grid-column: 5; }
  .page-topics .entry-state {
    grid-column: 6;
    justify-self: start;
  }
}

/* ---------- 编号体系 ---------- */
.page-topics .codes-layout {
  display: grid;
  gap: var(--space-6);
  margin-top: var(--space-6);
}

@media (min-width: 1024px) {
  .page-topics .codes-layout {
    grid-template-columns: minmax(0, 1.35fr) minmax(0, 1fr);
    gap: var(--space-8);
    align-items: start;
  }
}

.page-topics .codes-rows .meta-row {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-1);
  padding: var(--space-3) 0;
  border-bottom: var(--border-thin) solid var(--color-line);
}

@media (min-width: 640px) {
  .page-topics .codes-rows .meta-row {
    grid-template-columns: 140px minmax(0, 1fr);
    gap: var(--space-3);
  }
}

.page-topics .codes-rows .meta-key {
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.02em;
  color: var(--color-primary);
}

.page-topics .codes-rows .meta-value {
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
}

.page-topics .codes-rows a {
  color: var(--color-primary);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

.page-topics .codes-sample {
  padding: var(--space-4);
  border-radius: var(--radius-lg);
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
}

.page-topics .codes-sample-line {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: var(--space-1);
  margin: 0 0 var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-2xl);
  line-height: 1.15;
  letter-spacing: -0.02em;
}

.page-topics .cs-topic { color: var(--color-contrast-accent); }
.page-topics .cs-cat { color: var(--color-primary); }
.page-topics .cs-fb { color: var(--color-contrast-ink); }

.page-topics .cs-sep {
  font-size: var(--text-lg);
  color: var(--color-contrast-line);
}

.page-topics .codes-sample-note {
  margin: 0;
  font-size: var(--text-sm);
  line-height: var(--leading-body);
  color: color-mix(in srgb, var(--color-contrast-ink) 80%, transparent);
}

/* ---------- 维护节奏 ---------- */
.page-topics .update-grid {
  display: grid;
  gap: var(--space-6);
  margin-top: var(--space-6);
}

@media (min-width: 768px) {
  .page-topics .update-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

.page-topics .update-item {
  padding-top: var(--space-3);
  border-top: 3px solid var(--color-primary);
}

.page-topics .update-item .update-title {
  margin: 0 0 var(--space-2);
  font-size: var(--text-lg);
  line-height: 1.3;
  font-weight: var(--weight-heading);
  color: var(--color-ink);
}

.page-topics .update-item p {
  margin: 0;
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
}

.page-topics .update-item a,
.page-topics .update-tail a {
  color: var(--color-primary);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

.page-topics .update-tail {
  margin: var(--space-6) 0 0;
  padding-top: var(--space-3);
  max-width: var(--measure);
  border-top: var(--border-thin) solid var(--color-line);
  font-size: var(--text-sm);
  line-height: var(--leading-body);
  color: var(--color-ink-muted);
}

/* ---------- 键盘与降级 ---------- */
.page-topics .num-grid a:focus-visible,
.page-topics .dir-rail-list a:focus-visible,
.page-topics .codes-rows a:focus-visible,
.page-topics .update-item a:focus-visible,
.page-topics .update-tail a:focus-visible,
.page-topics .breadcrumb a:focus-visible {
  outline: 2px solid var(--color-focus);
  outline-offset: 2px;
}

@media (prefers-reduced-motion: reduce) {
  .page-topics .num-grid a,
  .page-topics .entry,
  .page-topics .band-bar,
  .page-topics .dir-rail-list a {
    transition: none;
  }
}