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

.page-topics .cover-section {
  padding-block: var(--section-y);
}

@media (min-width: 900px) {
  .page-topics .cover-section {
    padding-block: var(--section-y-lg);
  }
}

.page-topics .breadcrumb {
  margin-bottom: var(--space-4);
}

/* ---------- 封面 ---------- */

.page-topics .cover {
  display: grid;
  gap: var(--space-4);
  align-items: start;
}

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

.page-topics .cover__index {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  border-top: var(--border-thin) solid var(--color-contrast-line);
  border-left: var(--border-thin) solid var(--color-contrast-line);
}

.page-topics .cover__index a {
  display: block;
  padding: var(--space-2) 0;
  text-align: center;
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: var(--weight-heading);
  letter-spacing: 0.04em;
  color: var(--color-contrast-ink);
  text-decoration: none;
  border-right: var(--border-thin) solid var(--color-contrast-line);
  border-bottom: var(--border-thin) solid var(--color-contrast-line);
  transition: background-color 160ms ease, color 160ms ease;
}

.page-topics .cover__index a:hover,
.page-topics .cover__index a:focus-visible {
  background: var(--color-primary);
  color: var(--color-primary-ink);
}

.page-topics .cover__main h1 {
  margin: 0;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-display);
  line-height: 0.94;
  letter-spacing: var(--tracking-heading);
  color: var(--color-contrast-ink);
}

.page-topics .cover__lede {
  margin: var(--space-3) 0 0;
  max-width: 54ch;
  font-size: var(--text-lg);
  line-height: 1.5;
  color: var(--color-contrast-ink);
  opacity: 0.84;
}

.page-topics .cover__filters {
  margin-top: var(--space-4);
}

.page-topics .cover__figure {
  margin: 0;
}

.page-topics .cover__figure .figure__media {
  border: var(--border-thin) solid var(--color-contrast-line);
  background: var(--color-contrast-surface);
}

.page-topics .cover__figure .figure__caption {
  color: var(--color-contrast-ink);
  opacity: 0.6;
}

@media (min-width: 900px) {
  .page-topics .cover {
    grid-template-columns: 96px minmax(0, 1fr);
    column-gap: var(--space-6);
    row-gap: var(--space-8);
  }

  .page-topics .cover__index {
    grid-column: 1;
    grid-row: 1 / span 2;
    grid-template-columns: minmax(0, 1fr);
  }

  .page-topics .cover__index a {
    padding: var(--space-2) 0;
    font-size: var(--text-lg);
  }

  .page-topics .cover__main {
    grid-column: 2;
    grid-row: 1;
  }

  .page-topics .cover__figure {
    grid-column: 2;
    grid-row: 2;
  }
}

/* ---------- 筛选条 ---------- */

.page-topics .filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.page-topics .filter-btn {
  appearance: none;
  border: var(--border-thin) solid var(--color-contrast-line);
  border-radius: var(--radius-pill);
  background: transparent;
  color: var(--color-contrast-ink);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  padding: var(--space-1) var(--space-2);
  cursor: pointer;
  transition: background-color 160ms ease, color 160ms ease, border-color 160ms ease;
}

.page-topics .filter-btn:hover {
  background: var(--color-primary-ink);
  color: var(--color-contrast-surface);
  border-color: var(--color-primary-ink);
}

.page-topics .filter-btn[aria-pressed="true"] {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--color-primary-ink);
}

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

.page-topics .filter-status {
  margin: var(--space-2) 0 0;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  color: var(--color-contrast-ink);
  opacity: 0.58;
}

/* ---------- 斜向数据带 ---------- */

.page-topics .cover-strip {
  margin-top: var(--space-8);
  background: var(--color-primary);
  color: var(--color-primary-ink);
  padding: var(--space-4) 0;
  transform: skewY(-1.4deg);
}

.page-topics .cover-strip__inner {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-4) var(--space-3);
  transform: skewY(1.4deg);
}

.page-topics .cover-strip__value {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--text-2xl);
  font-weight: var(--weight-heading);
  line-height: 1;
  letter-spacing: -0.03em;
}

.page-topics .cover-strip__label {
  display: block;
  margin-top: var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.14em;
  opacity: 0.82;
}

@media (min-width: 720px) {
  .page-topics .cover-strip__inner {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

@media (min-width: 900px) {
  .page-topics .cover-strip__value {
    font-size: var(--text-3xl);
  }
}

/* ---------- 分组头部 ---------- */

.page-topics .group-head {
  display: grid;
  gap: var(--space-2);
}

.page-topics .group-head__num {
  font-family: var(--font-mono);
  font-size: var(--text-xl);
  font-weight: var(--weight-heading);
  line-height: 1;
  letter-spacing: -0.03em;
  color: var(--color-accent);
}

.page-topics .group-head .section-title {
  margin: var(--space-1) 0 0;
  font-size: var(--text-2xl);
}

.page-topics .group-head__lede {
  margin: var(--space-2) 0 0;
  max-width: var(--measure);
  color: var(--color-ink-soft);
}

.page-topics .section--contrast .group-head__num,
.page-topics .section--primary .group-head__num {
  color: var(--color-contrast-accent);
}

.page-topics .section--contrast .group-head .section-title,
.page-topics .section--primary .group-head .section-title {
  color: var(--color-contrast-ink);
}

.page-topics .section--contrast .group-head__lede,
.page-topics .section--primary .group-head__lede {
  color: var(--color-contrast-ink);
  opacity: 0.82;
}

@media (min-width: 720px) {
  .page-topics .group-head {
    grid-template-columns: 96px minmax(0, 1fr);
    column-gap: var(--space-6);
    align-items: start;
  }
}

/* ---------- 分组主体 ---------- */

.page-topics .group-body {
  display: grid;
  gap: var(--space-6);
  margin-top: var(--space-6);
}

.page-topics .group-figure {
  margin: 0;
}

.page-topics .group-figure .figure__media {
  border: var(--border-thin) solid var(--color-line);
  background: var(--color-surface-deep);
}

.page-topics .section--contrast .group-figure .figure__media,
.page-topics .section--primary .group-figure .figure__media {
  border-color: var(--color-contrast-line);
  background: var(--color-contrast-surface);
}

.page-topics .section--contrast .group-figure .figure__caption,
.page-topics .section--primary .group-figure .figure__caption {
  color: var(--color-contrast-ink);
  opacity: 0.62;
}

@media (min-width: 900px) {
  .page-topics .group-body {
    grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
    column-gap: var(--space-8);
    margin-top: var(--space-8);
  }
}

/* ---------- 条目列表 ---------- */

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

.page-topics .section--contrast .topic-list,
.page-topics .section--primary .topic-list {
  border-bottom-color: var(--color-contrast-line);
}

.page-topics .topic-entry {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  column-gap: var(--space-3);
  padding: var(--space-3) var(--space-2);
  border-top: var(--border-thin) solid var(--color-line);
  color: var(--color-ink);
  scroll-margin-top: 120px;
  transition: background-color 180ms cubic-bezier(0.2, 0.7, 0.2, 1), color 180ms cubic-bezier(0.2, 0.7, 0.2, 1);
}

.page-topics .section--contrast .topic-entry,
.page-topics .section--primary .topic-entry {
  border-top-color: var(--color-contrast-line);
  color: var(--color-contrast-ink);
}

.page-topics .topic-entry__num {
  grid-column: 1;
  grid-row: 1 / span 3;
  font-family: var(--font-mono);
  font-size: var(--text-lg);
  font-weight: var(--weight-heading);
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--color-accent);
  padding-top: 3px;
}

.page-topics .topic-entry__title {
  grid-column: 2;
  margin: 0;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  line-height: 1.22;
  letter-spacing: var(--tracking-heading);
  color: inherit;
}

.page-topics .topic-entry__desc {
  grid-column: 2;
  margin: var(--space-1) 0 0;
  font-size: var(--text-sm);
  line-height: 1.75;
  color: inherit;
  opacity: 0.72;
}

.page-topics .topic-entry__desc a {
  color: inherit;
  text-decoration: underline;
  text-underline-offset: 3px;
}

.page-topics .topic-entry__meta {
  grid-column: 2;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1) var(--space-2);
  margin: var(--space-2) 0 0;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  color: inherit;
  opacity: 0.6;
}

.page-topics .topic-entry .tag {
  display: inline-block;
  padding: 0 var(--space-1);
  border: var(--border-thin) solid currentColor;
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  white-space: nowrap;
  color: var(--color-accent);
}

.page-topics .section--contrast .topic-entry .tag,
.page-topics .section--primary .topic-entry .tag {
  color: var(--color-contrast-accent);
}

@media (hover: hover) {
  .page-topics .topic-entry:hover {
    background: var(--color-primary);
    color: var(--color-primary-ink);
  }

  .page-topics .topic-entry:hover .topic-entry__num,
  .page-topics .topic-entry:hover .tag {
    color: var(--color-primary-ink);
  }

  .page-topics .topic-entry:hover .topic-entry__desc,
  .page-topics .topic-entry:hover .topic-entry__meta {
    opacity: 0.86;
  }

  .page-topics .section--contrast .topic-entry:hover,
  .page-topics .section--primary .topic-entry:hover {
    background: var(--color-surface);
    color: var(--color-ink);
  }

  .page-topics .section--contrast .topic-entry:hover .topic-entry__num,
  .page-topics .section--contrast .topic-entry:hover .tag,
  .page-topics .section--primary .topic-entry:hover .topic-entry__num,
  .page-topics .section--primary .topic-entry:hover .tag {
    color: var(--color-accent);
  }
}

.page-topics .topic-entry:focus-within {
  outline: var(--border-thick) solid var(--color-focus);
  outline-offset: -2px;
}

/* ---------- 说明区 ---------- */

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

.page-topics .note-block__title {
  margin: 0 0 var(--space-2);
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-xl);
  line-height: 1.18;
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
}

.page-topics .note-block .prose {
  margin: 0;
  max-width: var(--measure);
  color: var(--color-ink-soft);
}

.page-topics .note-block .prose a {
  color: var(--color-primary);
  text-decoration: underline;
  text-underline-offset: 3px;
}

@media (min-width: 900px) {
  .page-topics .note-grid {
    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
    column-gap: var(--space-8);
  }
}

/* ---------- 图片通用 ---------- */

.page-topics img {
  max-width: 100%;
  height: auto;
  display: block;
}

.page-topics .figure__media img {
  width: 100%;
  object-fit: cover;
}

@media (prefers-reduced-motion: reduce) {
  .page-topics .cover-strip,
  .page-topics .cover-strip__inner {
    transform: none;
  }
}
</main>