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

.page-about .section {
  padding: var(--section-y) 0;
}

.page-about .section--lg {
  padding: var(--section-y-lg) 0;
}

.page-about .section--tight {
  padding: calc(var(--section-y) / 2) 0;
}

/* ---------- 面包屑 ---------- */
.page-about .breadcrumb {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  padding-top: var(--space-4);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
}

.page-about .breadcrumb a {
  color: var(--color-ink-muted);
  text-decoration: none;
  padding-bottom: 1px;
  border-bottom: var(--border-thin) solid var(--color-line);
  transition: color 160ms linear, border-color 160ms linear;
}

.page-about .breadcrumb a:hover,
.page-about .breadcrumb a:focus-visible {
  color: var(--color-primary);
  border-bottom-color: var(--color-primary);
}

.page-about .breadcrumb [aria-current="page"] {
  color: var(--color-ink);
}

/* ---------- 开篇 ---------- */
.page-about .story-open-grid {
  align-items: start;
  row-gap: var(--space-6);
}

.page-about .story-title {
  margin: 0 0 var(--space-3);
  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);
}

.page-about .story-lede {
  margin: 0 0 var(--space-4);
  padding-left: var(--space-3);
  border-left: var(--border-thick) solid var(--color-primary);
  font-size: var(--text-lg);
  line-height: 1.68;
  color: var(--color-ink);
  max-width: var(--measure);
}

.page-about .story-text {
  margin: 0 0 var(--space-3);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink);
  max-width: var(--measure);
}

.page-about .story-text:last-child {
  margin-bottom: 0;
}

.page-about .story-open-media {
  position: relative;
  z-index: 2;
}

/* ---------- 通用媒体容器 ---------- */
.page-about .media {
  position: relative;
  display: block;
  margin: 0;
  overflow: hidden;
  max-width: 100%;
  border: var(--border-thin) solid var(--color-line);
  border-radius: var(--radius-sm);
  background-color: var(--color-surface-alt);
}

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

.page-about .story-open-media .media img {
  aspect-ratio: 16 / 9;
}

.page-about .team-media .media img {
  aspect-ratio: 8 / 5;
}

.page-about .close-media .media img {
  aspect-ratio: 3 / 2;
}

.page-about .media-caption {
  position: absolute;
  inset: auto 0 0 0;
  margin: 0;
  padding: var(--space-2) var(--space-3);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.06em;
  color: var(--color-contrast-ink);
  background: var(--overlay-scrim);
}

/* ---------- 章节头补充 ---------- */
.page-about .story-head {
  margin-bottom: var(--space-6);
}

.page-about .story-head .section-title {
  max-width: 24ch;
}

/* ---------- 阶段横条 ---------- */
.page-about .phase-list {
  list-style: none;
  margin: 0;
  padding: var(--space-4) 0 0;
  border-top: var(--border-thin) solid var(--color-line);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.page-about .phase {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-2);
  padding: var(--space-3);
  border-left: 4px solid var(--color-line);
  border-radius: var(--radius-sm);
  transition: transform 160ms linear, border-left-width 160ms linear, background-color 160ms linear;
  outline-offset: 3px;
}

.page-about .phase:hover,
.page-about .phase:focus-visible {
  transform: translateX(4px);
  border-left-width: 7px;
}

.page-about .phase:focus-visible {
  outline: var(--border-thick) solid var(--color-focus);
}

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

.page-about .phase--alt {
  background-color: var(--color-surface-alt);
  border-left-color: var(--color-ink-muted);
}

.page-about .phase--plain {
  background-color: transparent;
  border-left-color: var(--color-line);
}

.page-about .phase--dark {
  background-color: var(--color-contrast-surface);
  border-left-color: var(--color-contrast-accent);
}

.page-about .phase--dark .phase-name,
.page-about .phase--dark .phase-field dd {
  color: var(--color-contrast-ink);
}

.page-about .phase--dark .phase-field dt {
  color: var(--color-contrast-ink);
  opacity: 0.72;
}

.page-about .phase--dark .phase-num {
  color: var(--color-contrast-accent);
}

.page-about .phase--dark a {
  color: var(--color-contrast-accent);
  border-bottom-color: var(--color-contrast-accent);
}

.page-about .phase-num {
  display: block;
  margin-bottom: var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--color-primary);
  font-variant-numeric: tabular-nums;
}

.page-about .phase--alt .phase-num {
  color: var(--color-ink-muted);
}

.page-about .phase-name {
  margin: 0;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-xl);
  line-height: var(--leading-heading);
  color: var(--color-ink);
}

.page-about .phase-fields {
  margin: 0;
  display: grid;
  gap: var(--space-2);
}

.page-about .phase-field {
  display: grid;
  grid-template-columns: 1fr;
  gap: 4px;
}

.page-about .phase-field dt {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.12em;
  color: var(--color-ink-muted);
  font-variant-numeric: tabular-nums;
}

.page-about .phase-field dd {
  margin: 0;
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--color-ink);
}

.page-about .phase-field a,
.page-about .close-copy a {
  color: var(--color-primary);
  text-decoration: none;
  border-bottom: var(--border-thin) solid var(--color-primary);
  transition: color 160ms linear, border-color 160ms linear;
}

.page-about .phase-field a:hover,
.page-about .close-copy a:hover,
.page-about .phase-field a:focus-visible,
.page-about .close-copy a:focus-visible {
  color: var(--color-ink);
  border-bottom-color: var(--color-ink);
}

/* ---------- 能力边界 ---------- */
.page-about .bounds-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: var(--space-6);
}

.page-about .bound {
  border-left: 4px solid var(--color-accent);
  padding: var(--space-1) 0 var(--space-1) var(--space-3);
}

.page-about .bound-label {
  margin: 0 0 var(--space-1);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-ink-muted);
  font-variant-numeric: tabular-nums;
}

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

.page-about .bound-text {
  margin: 0;
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink-soft);
  max-width: 48ch;
}

/* ---------- 运营原则 ---------- */
.page-about .principles {
  border-top: var(--border-thin) solid var(--color-line);
}

.page-about .principle {
  border-bottom: var(--border-thin) solid var(--color-line);
}

.page-about .principle-summary {
  display: flex;
  align-items: baseline;
  gap: var(--space-3);
  padding: var(--space-3) 0;
  cursor: pointer;
  list-style: none;
}

.page-about .principle-summary::-webkit-details-marker {
  display: none;
}

.page-about .principle-summary::marker {
  content: "";
}

.page-about .principle-num {
  flex: 0 0 auto;
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-primary);
  font-variant-numeric: tabular-nums;
}

.page-about .principle-title {
  flex: 1 1 auto;
  font-family: var(--font-heading);
  font-weight: var(--weight-heading);
  font-size: var(--text-xl);
  line-height: var(--leading-heading);
  color: var(--color-ink);
  transition: color 160ms linear;
}

.page-about .principle-summary:hover .principle-title,
.page-about .principle-summary:focus-visible .principle-title {
  color: var(--color-primary);
}

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

.page-about .principle-summary::after {
  content: "+";
  flex: 0 0 auto;
  font-family: var(--font-mono);
  font-size: var(--text-lg);
  line-height: 1;
  color: var(--color-ink-muted);
}

.page-about .principle[open] .principle-summary::after {
  content: "−";
}

.page-about .principle-body {
  padding: 0 0 var(--space-4) var(--space-6);
  max-width: var(--measure);
}

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

/* ---------- 团队 ---------- */
.page-about .team-grid,
.page-about .close-grid {
  align-items: start;
  row-gap: var(--space-6);
}

.page-about .team-copy p,
.page-about .close-copy p {
  margin: 0 0 var(--space-3);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  color: var(--color-ink);
  max-width: 64ch;
}

.page-about .team-copy p:last-child,
.page-about .close-copy p:last-child {
  margin-bottom: 0;
}

/* ---------- 收口刻度 ---------- */
.page-about .story-rule {
  margin-top: var(--space-8);
  padding-top: var(--space-3);
}

.page-about .rule-scale {
  height: 10px;
  border-top: var(--border-thin) solid var(--color-ink-muted);
  background-image: repeating-linear-gradient(
    to right,
    var(--color-ink-muted) 0,
    var(--color-ink-muted) 1px,
    transparent 1px,
    transparent 40px
  );
  background-size: 100% 6px;
  background-repeat: no-repeat;
  background-position: 0 0;
}

.page-about .story-rule .mono-label {
  display: block;
  margin: var(--space-2) 0 0;
}

/* ---------- 桌面 ---------- */
@media (min-width: 560px) {
  .page-about .phase-field {
    grid-template-columns: 88px 1fr;
    gap: var(--space-2);
    align-items: baseline;
  }
}

@media (min-width: 860px) {
  .page-about .phase-list {
    gap: var(--space-4);
  }

  .page-about .phase {
    grid-template-columns: minmax(0, 3fr) minmax(0, 7fr);
    gap: var(--space-4);
    padding: var(--space-4) var(--space-4) var(--space-4) var(--space-3);
    align-items: start;
  }

  .page-about .phase:nth-child(2) {
    grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
    width: 93%;
    margin-left: auto;
  }

  .page-about .phase:nth-child(3) {
    grid-template-columns: minmax(0, 4fr) minmax(0, 8fr);
    width: 97%;
  }

  .page-about .phase:nth-child(4) {
    grid-template-columns: minmax(0, 3fr) minmax(0, 9fr);
    width: 95%;
    margin-left: auto;
  }

  .page-about .phase:nth-child(5) {
    width: 100%;
  }

  .page-about .phase:nth-child(6) {
    grid-template-columns: minmax(0, 4fr) minmax(0, 8fr);
    width: 91%;
    margin-left: var(--space-4);
  }

  .page-about .bounds-list {
    grid-template-columns: repeat(12, 1fr);
    column-gap: var(--gutter);
    row-gap: var(--space-6);
  }

  .page-about .bound:nth-child(1) {
    grid-column: 1 / span 6;
  }

  .page-about .bound:nth-child(2) {
    grid-column: 7 / span 6;
  }

  .page-about .bound:nth-child(3) {
    grid-column: 3 / span 7;
  }
}

@media (min-width: 900px) {
  .page-about .story-open-copy .story-lede,
  .page-about .story-open-copy .story-text {
    max-width: 56ch;
  }

  .page-about .story-open-media {
    margin-top: var(--space-8);
    margin-left: calc(var(--space-6) * -1);
  }

  .page-about .team-media {
    position: relative;
    z-index: 1;
    margin-top: var(--space-6);
  }

  .page-about .team-copy {
    padding-left: var(--space-6);
  }

  .page-about .close-media {
    margin-top: var(--space-6);
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .phase,
  .page-about .principle-title,
  .page-about .breadcrumb a,
  .page-about .phase-field a,
  .page-about .close-copy a {
    transition: none;
  }

  .page-about .phase:hover,
  .page-about .phase:focus-visible {
    transform: none;
  }
}