.page-about {
  display: block;
  background: var(--color-surface);
  color: var(--color-ink);
}

/* 面包屑 */
.page-about .about-crumb {
  padding-top: var(--space-4);
}

/* ===== 首屏 ===== */
.page-about .about-hero {
  padding-top: var(--space-4);
  padding-bottom: var(--space-6);
}

.page-about .about-hero__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-4);
}

.page-about .about-hero__title {
  margin: var(--space-2) 0 0;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-3xl);
  line-height: var(--leading-heading);
  letter-spacing: var(--tracking-heading);
  color: var(--color-ink);
  overflow-wrap: anywhere;
}

.page-about .about-hero__text .lead {
  margin-top: var(--space-3);
}

.page-about .about-note {
  margin: var(--space-4) 0 0;
  padding: var(--space-2) var(--space-3);
  border-left: var(--border-thick) solid var(--color-primary);
  background: var(--color-primary-soft);
  border-radius: var(--radius-sm);
  font-size: var(--text-sm);
  line-height: 1.7;
  color: var(--color-ink);
  max-width: var(--measure);
}

.page-about .about-hero__visual {
  max-width: 560px;
}

/* ===== 图片 ===== */
.page-about .about-photo {
  position: relative;
  margin: 0;
  overflow: hidden;
  border-radius: var(--radius-md);
  background: var(--color-surface-alt);
}

.page-about .about-photo img {
  display: block;
  width: 100%;
  height: 100%;
  max-width: 100%;
  object-fit: cover;
}

.page-about .about-photo::after {
  content: "";
  position: absolute;
  inset: 0;
  background: color-mix(in srgb, var(--color-primary) 24%, transparent);
  mix-blend-mode: multiply;
  pointer-events: none;
}

.page-about .about-photo--landscape {
  aspect-ratio: 3 / 2;
}

.page-about .about-photo--std {
  aspect-ratio: 4 / 3;
  max-width: 520px;
}

.page-about .chapter__body .about-photo {
  margin-top: var(--space-4);
  margin-bottom: var(--space-1);
}

.page-about .about-caption {
  display: block;
  margin-top: var(--space-1);
  font-size: var(--text-sm);
  line-height: 1.6;
  color: var(--color-ink-muted);
  max-width: var(--measure);
}

/* ===== 章节 ===== */
.page-about .chapter {
  position: relative;
}

.page-about .chapter + .chapter {
  border-top: calc(var(--border-thin) / 2) solid var(--color-line);
}

.page-about .chapter__head {
  position: relative;
}

.page-about .chapter__num {
  display: block;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-2xl);
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--color-surface-deep);
  transition: color 160ms linear;
}

.page-about .chapter[data-active="true"] .chapter__num {
  color: var(--color-primary);
}

.page-about .chapter__title {
  margin: var(--space-2) 0 0;
  color: var(--color-ink);
}

.page-about .chapter__lede {
  margin: var(--space-2) 0 0;
  max-width: var(--measure);
  font-size: var(--text-lg);
  line-height: 1.6;
  color: var(--color-ink-soft);
}

.page-about .chapter__body {
  margin-top: var(--space-4);
}

.page-about .chapter__body p {
  max-width: var(--measure);
}

/* ===== 引用条 ===== */
.page-about .about-quote {
  margin: var(--space-6) 0 0;
  padding: var(--space-3) var(--space-4);
  background: var(--color-primary-soft);
  border-left: var(--border-thick) solid var(--color-primary);
  border-radius: var(--radius-sm);
  max-width: var(--measure);
}

.page-about .about-quote p {
  margin: 0;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-lg);
  line-height: 1.5;
  color: var(--color-ink);
}

/* ===== 阶段线 ===== */
.page-about .stage-flow {
  margin-top: var(--space-6);
}

.page-about .stage-tagbar {
  position: relative;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-2) 0;
}

.page-about .stage-tagbar::before {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  top: 50%;
  height: calc(var(--border-thin) / 2);
  background: var(--color-line);
  z-index: 0;
}

.page-about .stage-node {
  position: relative;
  z-index: 1;
  min-height: 44px;
}

.page-about .stage-node[aria-pressed="false"] {
  background: var(--color-surface);
}

.page-about .stage-node:focus-visible {
  outline: var(--border-thick) solid var(--color-focus);
  outline-offset: 2px;
}

.page-about .filter-count {
  margin: var(--space-2) 0 0;
  font-size: var(--text-sm);
  color: var(--color-ink-soft);
}

.page-about .stage-entries {
  margin-top: var(--space-4);
}

/* ===== 城市坐标列表 ===== */
.page-about .city-list {
  margin-top: var(--space-4);
}

/* ===== 出口 ===== */
.page-about .exit-list {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-3);
  max-width: 760px;
}

.page-about .exit {
  display: block;
  padding: var(--space-3);
  border: calc(var(--border-thin) / 2) solid var(--color-line);
  border-left: var(--border-thick) solid var(--color-primary);
  border-radius: var(--radius-sm);
  background: var(--color-surface-alt);
  color: var(--color-ink);
  text-decoration: none;
  min-height: 44px;
  overflow-wrap: anywhere;
  transition: background-color 160ms linear, border-color 160ms linear;
}

.page-about .exit:hover {
  background: var(--color-primary-soft);
  border-color: var(--color-primary);
}

.page-about .exit:focus-visible {
  outline: var(--border-thick) solid var(--color-focus);
  outline-offset: 2px;
}

.page-about .exit__key {
  display: block;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-xl);
  line-height: 1.3;
}

.page-about .exit__desc {
  display: block;
  margin-top: var(--space-1);
  font-size: var(--text-base);
  line-height: 1.7;
  color: var(--color-ink-soft);
}

/* ===== 桌面栅格与错位 ===== */
@media (min-width: 900px) {
  .page-about .about-hero__grid {
    grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
    column-gap: var(--gutter);
    align-items: start;
  }

  .page-about .about-hero__visual {
    max-width: none;
    margin-top: var(--space-8);
  }

  .page-about .chapter__head {
    display: grid;
    grid-template-columns: 104px minmax(0, 1fr);
    column-gap: var(--space-3);
    align-items: start;
  }

  .page-about .chapter__num {
    grid-column: 1;
    grid-row: 1 / span 2;
    font-size: var(--text-4xl);
  }

  .page-about .chapter__title {
    grid-column: 2;
    grid-row: 1;
    margin-top: 0;
  }

  .page-about .chapter__lede {
    grid-column: 2;
    grid-row: 2;
  }

  .page-about .chapter__body {
    padding-left: calc(104px + var(--space-3));
  }

  .page-about .exit-list {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .page-about .exit:first-child {
    grid-column: 1 / -1;
  }
}

@media (min-width: 1200px) {
  .page-about .city-list {
    column-gap: 0;
  }
}

@media (max-width: 620px) {
  .page-about .stage-tagbar {
    flex-direction: column;
    align-items: stretch;
  }

  .page-about .stage-tagbar::before {
    display: none;
  }

  .page-about .stage-node {
    width: 100%;
    text-align: left;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .chapter__num,
  .page-about .exit {
    transition: none;
  }
}