.page-topics {
  --topics-num-col: 56px;
  --topics-entry-gap: var(--space-2);
}

/* ---------- 首屏 ---------- */
.page-topics .topics-hero {
  background: var(--color-contrast-surface);
  color: var(--color-contrast-ink);
  padding-block: var(--space-4) var(--space-8);
  border-bottom: 2px solid var(--color-primary);
}

.page-topics .topics-hero__crumb {
  color: var(--color-ink-muted);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  margin-bottom: var(--space-4);
}

.page-topics .topics-hero__crumb a {
  color: var(--color-contrast-ink);
  text-decoration: none;
}

.page-topics .topics-hero__crumb a:hover {
  text-decoration: underline;
}

.page-topics .topics-hero__eyebrow {
  color: var(--color-contrast-accent);
  margin-bottom: var(--space-2);
}

.page-topics .topics-hero__title {
  font-family: var(--font-heading);
  font-size: var(--text-display);
  font-weight: var(--weight-heading);
  line-height: 1.05;
  letter-spacing: 0.06em;
  margin: 0 0 var(--space-6);
  max-width: 16em;
}

.page-topics .topics-hero__split {
  display: grid;
  gap: var(--space-6);
  align-items: end;
  padding-top: var(--space-4);
  border-top: 1px solid var(--color-contrast-line);
}

.page-topics .topics-hero__lede {
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-contrast-ink);
  max-width: 42ch;
  margin: 0 0 var(--space-4);
}

.page-topics .topics-hero__stats {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3) var(--space-6);
}

.page-topics .topics-hero__stats .stat {
  display: flex;
  flex-direction: column;
  gap: 2px;
  padding-left: var(--space-2);
  border-left: 1px solid var(--color-contrast-line);
}

.page-topics .topics-hero__stats .stat__value {
  font-size: var(--text-xl);
  font-weight: var(--weight-heading);
  color: var(--color-contrast-ink);
  line-height: 1.1;
}

.page-topics .topics-hero__stats .stat__label {
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
}

.page-topics .topics-hero__figure {
  margin: 0;
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--color-contrast-line);
}

.page-topics .topics-hero__figure img {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 16 / 9;
  object-fit: cover;
}

.page-topics .topics-hero__figure .media-frame__caption {
  color: var(--color-contrast-ink);
  background: var(--color-contrast-surface);
  border-top: 1px solid var(--color-contrast-line);
  font-size: var(--text-xs);
  padding: var(--space-1) var(--space-2);
  margin: 0;
}

.page-topics .topics-hero__tags {
  list-style: none;
  margin: var(--space-6) 0 0;
  padding: var(--space-3) 0 0;
  border-top: 1px solid var(--color-contrast-line);
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.page-topics .topics-hero__tags li {
  font-size: var(--text-sm);
  letter-spacing: 0.08em;
  padding: 6px 14px;
  border: 1px solid var(--color-contrast-line);
  border-radius: var(--radius-pill);
  color: var(--color-contrast-ink);
}

/* ---------- 目录主体 ---------- */
.page-topics .topics-catalog__head {
  max-width: var(--measure);
}

.page-topics .topics-catalog__intro {
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
  margin: var(--space-3) 0 var(--space-6);
}

.page-topics .topics-filter {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  padding: var(--space-3) 0;
  border-top: 1px solid var(--color-line);
}

.page-topics .topics-filter:last-of-type {
  border-bottom: 1px solid var(--color-line);
}

.page-topics .topics-filter__label {
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
  margin: 0;
}

.page-topics .topics-filter .filter-btn {
  border-radius: var(--radius-pill);
  border: 1px solid var(--color-line);
  background: var(--color-surface-deep);
  color: var(--color-ink);
  font-size: var(--text-sm);
  padding: 7px 16px;
  cursor: pointer;
  transition: background-color 140ms ease, border-color 140ms ease, color 140ms ease;
}

.page-topics .topics-filter .filter-btn:hover {
  background: var(--color-primary-soft);
}

.page-topics .topics-filter .filter-btn[aria-pressed="true"] {
  background: var(--color-highlight);
  border-color: var(--color-accent);
  color: var(--color-accent);
  font-weight: 500;
}

.page-topics .topics-filter .filter-btn:focus-visible {
  outline: 2px solid var(--color-focus);
  outline-offset: 2px;
}

.page-topics .topics-filter__count {
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
  margin: var(--space-3) 0 var(--space-4);
  font-variant-numeric: tabular-nums;
}

/* ---------- 分组 ---------- */
.page-topics .topics-groups {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

.page-topics .topic-group {
  scroll-margin-top: var(--space-8);
}

.page-topics .topic-group__head {
  display: grid;
  gap: var(--space-3);
  align-items: center;
  margin-bottom: var(--space-3);
}

.page-topics .topic-group__note {
  font-size: var(--text-base);
  line-height: 1.7;
  color: var(--color-ink-soft);
  max-width: 60ch;
  margin: var(--space-2) 0 0;
}

.page-topics .topic-group__figure {
  margin: 0;
  border-radius: var(--radius-md);
  overflow: hidden;
  border: 1px solid var(--color-line);
}

.page-topics .topic-group__figure img {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 3 / 2;
  object-fit: cover;
}

.page-topics .topic-list {
  list-style: none;
  margin: 0;
  padding: 0;
  border-top: 1px solid var(--color-line);
}

.page-topics .topics-entry {
  display: grid;
  grid-template-columns: var(--topics-num-col) minmax(0, 1fr);
  gap: var(--topics-entry-gap);
  padding: var(--space-3) 0;
  border-bottom: 1px solid var(--color-line);
  transition: background-color 140ms ease;
}

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

.page-topics .topics-entry__num {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--color-primary);
  line-height: 1.2;
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.04em;
}

.page-topics .topics-entry__body {
  min-width: 0;
}

.page-topics .topics-entry__meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1);
  margin-bottom: var(--space-1);
}

.page-topics .topics-status {
  background: var(--color-primary-soft);
  color: var(--color-primary);
  border: 1px solid transparent;
}

.page-topics .topics-status--serial {
  background: var(--color-highlight);
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.page-topics .topics-status--archived {
  background: var(--color-surface-deep);
  border-color: var(--color-line);
  color: var(--color-ink-muted);
}

.page-topics .topics-cat {
  background: transparent;
  border: 1px solid var(--color-line);
  color: var(--color-ink-soft);
}

.page-topics .topics-entry__freq {
  margin-left: auto;
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: var(--color-ink-muted);
  opacity: 0.7;
  transition: opacity 140ms ease, color 140ms ease;
}

.page-topics .topics-entry:hover .topics-entry__freq {
  opacity: 1;
  color: var(--color-primary);
}

.page-topics .topics-entry__title {
  font-size: var(--text-lg);
  font-weight: 500;
  line-height: 1.35;
  letter-spacing: 0.04em;
  color: var(--color-ink);
  margin: 0 0 var(--space-1);
}

.page-topics .topics-entry__desc {
  font-size: var(--text-base);
  line-height: 1.7;
  color: var(--color-ink);
  margin: 0 0 4px;
  max-width: 68ch;
}

.page-topics .topics-entry__who {
  font-size: var(--text-sm);
  line-height: 1.6;
  color: var(--color-ink-muted);
  margin: 0;
}

/* ---------- 规则说明 ---------- */
.page-topics .topics-rules__layout {
  gap: var(--space-6);
}

.page-topics .topics-rules__lead .prose {
  margin-top: var(--space-3);
  color: var(--color-ink-soft);
}

.page-topics .topics-rules__list {
  list-style: none;
  margin: 0;
  padding: 0;
  counter-reset: rule;
  border-top: 2px solid var(--color-primary);
}

.page-topics .topics-rules__item {
  counter-increment: rule;
  display: grid;
  gap: 4px;
  padding: var(--space-3) 0 var(--space-3) var(--space-6);
  position: relative;
  border-bottom: 1px solid var(--color-line);
}

.page-topics .topics-rules__item::before {
  content: counter(rule, decimal-leading-zero);
  position: absolute;
  left: 0;
  top: var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  color: var(--color-primary);
  font-variant-numeric: tabular-nums;
}

.page-topics .topics-rules__item h3 {
  font-size: var(--text-base);
  font-weight: 500;
  letter-spacing: 0.06em;
  color: var(--color-ink);
  margin: 0;
}

.page-topics .topics-rules__item p {
  font-size: var(--text-base);
  line-height: 1.7;
  color: var(--color-ink-soft);
  margin: 0;
  max-width: 62ch;
}

/* ---------- 延伸阅读 ---------- */
.page-topics .topics-next__intro {
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
  max-width: 60ch;
  margin: var(--space-3) 0 var(--space-6);
}

.page-topics .topics-next__grid {
  gap: var(--space-3);
}

.page-topics .topics-next__card {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  padding: var(--space-4) var(--space-3);
  text-decoration: none;
  color: var(--color-ink);
  background: var(--color-surface);
  border: 1px solid var(--color-line);
  border-top: 3px solid var(--color-primary);
}

.page-topics .topics-next__card .eyebrow {
  color: var(--color-ink-muted);
}

.page-topics .topics-next__card-title {
  font-size: var(--text-lg);
  font-weight: 500;
  letter-spacing: 0.06em;
  color: var(--color-ink);
  margin: 0;
}

.page-topics .topics-next__card-text {
  font-size: var(--text-base);
  line-height: 1.7;
  color: var(--color-ink-soft);
  margin: 0;
}

.page-topics .topics-next__card .link-arrow {
  margin-top: auto;
  font-size: var(--text-sm);
  color: var(--color-accent);
  letter-spacing: 0.04em;
}

.page-topics .topics-next__back {
  margin-top: var(--space-6);
  padding-top: var(--space-3);
  border-top: 1px solid var(--color-line);
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}

.page-topics .topics-next__back a {
  color: var(--color-primary);
}

/* ---------- 响应式 ---------- */
@media (min-width: 720px) {
  .page-topics {
    --topics-num-col: 76px;
  }

  .page-topics .topics-filter {
    flex-direction: row;
    align-items: center;
    gap: var(--space-3);
  }

  .page-topics .topics-filter__label {
    flex: 0 0 64px;
  }

  .page-topics .topic-group__head {
    grid-template-columns: minmax(0, 1fr) 260px;
    gap: var(--space-6);
  }

  .page-topics .topics-entry__num {
    font-size: var(--text-xl);
  }

  .page-topics .topics-rules__item {
    grid-template-columns: 150px minmax(0, 1fr);
    gap: var(--space-3);
    align-items: baseline;
  }
}

@media (min-width: 1024px) {
  .page-topics .topics-hero {
    padding-block: var(--space-6) var(--section-y-lg);
  }

  .page-topics .topics-hero__split {
    grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
    gap: var(--space-8);
  }

  .page-topics .topics-hero__title {
    max-width: 14em;
  }

  .page-topics .topics-entry {
    grid-template-columns: var(--topics-num-col) minmax(0, 1fr);
    gap: var(--space-3);
  }

  .page-topics .topics-rules__layout {
    grid-template-columns: minmax(0, 4fr) minmax(0, 8fr);
    gap: var(--space-8);
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-topics .topics-entry,
  .page-topics .topics-entry__freq,
  .page-topics .topics-filter .filter-btn {
    transition: none;
  }
}