.page-about {
  --about-sec: 72px;
  --about-year-w: 58px;
  --about-gold-deep: #8A5A12;
  --about-paper-line: rgba(10, 18, 32, .14);
  --about-mute: rgba(201, 210, 220, .62);
  background: var(--ink-900);
  color: var(--silver-300);
  overflow-x: hidden;
}

@media (min-width: 768px) {
  .page-about { --about-year-w: 96px; }
}

@media (min-width: 1024px) {
  .page-about {
    --about-sec: 120px;
    --about-year-w: 132px;
  }
}

@media (min-width: 1280px) {
  .page-about { --about-year-w: 184px; }
}

/* ---------- 面包屑 ---------- */
.page-about .about-crumb ol {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0 8px;
  margin: 0;
  padding: 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .06em;
}

.page-about .about-crumb li {
  display: flex;
  align-items: center;
  min-height: 44px;
}

.page-about .about-crumb li + li::before {
  content: "/";
  margin-right: 8px;
  color: var(--about-mute);
}

.page-about .about-crumb a {
  color: var(--about-mute);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color 200ms var(--ease), border-color 200ms var(--ease);
}

.page-about .about-crumb a:hover,
.page-about .about-crumb a:focus-visible {
  color: var(--gold-250);
  border-bottom-color: var(--gold-500);
}

.page-about .about-crumb [aria-current="page"] {
  color: var(--silver-300);
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  isolation: isolate;
  padding: 24px 0 40px;
  background: var(--ink-900);
  border-bottom: var(--hair-soft);
}

.page-about .about-hero::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -2;
  background-image:
    linear-gradient(rgba(201, 210, 220, .05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(201, 210, 220, .05) 1px, transparent 1px);
  background-size: 24px 24px;
  -webkit-mask-image: radial-gradient(130% 90% at 15% 0%, #000 10%, transparent 76%);
  mask-image: radial-gradient(130% 90% at 15% 0%, #000 10%, transparent 76%);
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -1;
  background: radial-gradient(900px 540px at 84% 4%, rgba(16, 32, 58, .95), rgba(10, 18, 32, 0) 72%);
}

.page-about .about-hero__grid {
  display: grid;
  gap: 32px;
  margin-top: 24px;
}

.page-about .about-hero__lead {
  min-width: 0;
}

.page-about .about-hero h1 {
  margin: 18px 0 0;
  font-family: var(--font-serif);
  font-weight: 700;
  font-size: clamp(34px, 7.6vw, 61px);
  line-height: 1.1;
  letter-spacing: -.02em;
  color: var(--white);
}

.page-about .about-hero .lead {
  margin: 20px 0 0;
  max-width: 46ch;
  font-size: 16px;
  line-height: 1.85;
  color: var(--silver-300);
}

.page-about .about-index {
  list-style: none;
  display: grid;
  gap: 0;
  margin: 26px 0 0;
  padding: 0;
}

.page-about .about-index a {
  display: flex;
  align-items: center;
  gap: 12px;
  min-height: 44px;
  padding: 0 2px;
  font-size: 14px;
  letter-spacing: .04em;
  color: var(--silver-300);
  text-decoration: none;
  border-bottom: 1px solid rgba(201, 210, 220, .12);
  transition: color 200ms var(--ease), border-color 200ms var(--ease);
}

.page-about .about-index a:hover,
.page-about .about-index a:focus-visible {
  color: var(--gold-250);
  border-bottom-color: var(--gold-500);
}

.page-about .about-index .mono {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--gold-500);
  font-variant-numeric: tabular-nums;
}

.page-about .about-hero__figure {
  margin: 0;
  min-width: 0;
}

.page-about .about-frame {
  position: relative;
  overflow: hidden;
  background: var(--navy-800);
  border: var(--hair);
}

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

.page-about .about-frame--tall { aspect-ratio: 4 / 5; }
.page-about .about-frame--photo { aspect-ratio: 4 / 3; }
.page-about .about-frame--pano { aspect-ratio: 7 / 3; }

.page-about .media-frame__cap {
  display: block;
  margin-top: 12px;
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.6;
  letter-spacing: .06em;
  color: var(--about-mute);
}

.page-about .about-scale {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px 8px;
  margin: 34px 0 0;
  padding: 16px 0 0;
  border-top: var(--hair);
}

.page-about .about-scale li {
  position: relative;
  display: flex;
  align-items: baseline;
  gap: 8px;
  padding-top: 14px;
  font-size: 12px;
  letter-spacing: .06em;
  color: var(--about-mute);
}

.page-about .about-scale li::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 1px;
  height: 8px;
  background: var(--silver-300);
  opacity: .55;
}

.page-about .about-scale li .mono {
  font-family: var(--font-mono);
  font-size: 14px;
  color: var(--silver-300);
  font-variant-numeric: tabular-nums;
}

.page-about .about-scale li:last-child::before {
  background: var(--gold-500);
  opacity: 1;
}

.page-about .about-scale li:last-child .mono {
  color: var(--gold-250);
}

@media (min-width: 768px) {
  .page-about .about-scale {
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 0;
    margin-top: 48px;
  }
}

@media (min-width: 1024px) {
  .page-about .about-hero {
    padding: 32px 0 56px;
  }

  .page-about .about-hero__grid {
    grid-template-columns: minmax(0, 7fr) minmax(0, 4fr);
    gap: 64px;
    margin-top: 48px;
    align-items: start;
  }

  .page-about .about-hero__figure {
    margin-top: 8px;
  }

  .page-about .about-frame--tall { aspect-ratio: 3 / 4; }

  .page-about .about-scale { margin-top: 64px; }
}

/* ---------- 章节头 ---------- */
.page-about .about-sec-head {
  display: grid;
  gap: 14px;
  margin-bottom: 36px;
}

.page-about .about-sec-head h2 {
  margin: 0;
  max-width: 24ch;
  font-family: var(--font-serif);
  font-weight: 600;
  font-size: clamp(25px, 4.4vw, 39px);
  line-height: 1.18;
  letter-spacing: -.01em;
  color: var(--white);
}

.page-about .sec-note {
  margin: 0;
  max-width: 56ch;
  font-size: 14px;
  line-height: 1.8;
  color: var(--about-mute);
}

@media (min-width: 1024px) {
  .page-about .about-sec-head {
    gap: 18px;
    margin-bottom: 64px;
  }
}

/* ---------- 01 时间轴 ---------- */
.page-about .about-timeline {
  padding: var(--about-sec) 0;
  background: var(--ink-900);
}

.page-about .tl {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .tl-item {
  position: relative;
  padding: 0 0 44px 26px;
  border-left: var(--hair-soft);
}

.page-about .tl-item:last-child {
  padding-bottom: 0;
  border-left-color: transparent;
}

.page-about .tl-item::before {
  content: "";
  position: absolute;
  left: -3px;
  top: 13px;
  width: 6px;
  height: 6px;
  background: var(--gold-500);
  transform: rotate(45deg);
  box-shadow: 0 0 0 4px var(--ink-900);
}

.page-about .tl-year {
  margin: 0 0 12px;
  font-family: var(--font-mono);
  font-size: 31px;
  line-height: 1;
  letter-spacing: -.02em;
  color: var(--white);
  font-variant-numeric: tabular-nums;
}

.page-about .tl-entry summary {
  list-style: none;
  cursor: pointer;
  display: grid;
  gap: 8px;
  padding: 2px 0;
}

.page-about .tl-entry summary::-webkit-details-marker { display: none; }
.page-about .tl-entry summary::marker { content: ""; }

.page-about .tl-title {
  display: block;
  font-family: var(--font-serif);
  font-weight: 600;
  font-size: 20px;
  line-height: 1.4;
  color: var(--white);
}

.page-about .tl-teaser {
  display: block;
  max-width: 54ch;
  font-size: 14px;
  line-height: 1.8;
  color: var(--about-mute);
}

.page-about .tl-entry summary::after {
  content: "展开完整说明";
  justify-self: start;
  margin-top: 4px;
  padding-bottom: 2px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .08em;
  color: var(--gold-500);
  border-bottom: 1px solid rgba(217, 138, 43, .45);
  transition: color 200ms var(--ease), border-color 200ms var(--ease);
}

.page-about .tl-entry[open] summary::after {
  content: "收起说明";
  color: var(--about-mute);
  border-bottom-color: rgba(201, 210, 220, .25);
}

.page-about .tl-entry summary:focus-visible {
  outline: 2px solid var(--gold-500);
  outline-offset: 4px;
}

.page-about .tl-body {
  max-width: 66ch;
  margin-top: 20px;
  padding-top: 20px;
  border-top: var(--hair-soft);
}

.page-about .tl-body p {
  margin: 0 0 14px;
  font-size: 16px;
  line-height: 1.85;
  color: var(--silver-300);
}

.page-about .tl-body p:last-child { margin-bottom: 0; }

.page-about .tl-code {
  display: inline-block;
  margin-top: 4px;
  padding: 10px 14px;
  font-family: var(--font-mono);
  font-size: 14px;
  letter-spacing: .04em;
  color: var(--gold-250);
  background: rgba(16, 32, 58, .75);
  border: var(--hair-soft);
  border-left: 2px solid var(--gold-500);
  font-variant-numeric: tabular-nums;
}

.page-about .tl-figure {
  margin: 24px 0 0;
}

@media (min-width: 1024px) {
  .page-about .tl-item {
    display: grid;
    grid-template-columns: var(--about-year-w) minmax(0, 1fr);
    column-gap: 56px;
    padding: 0 0 80px;
    border-left: 0;
  }

  .page-about .tl-item:last-child { padding-bottom: 0; }

  .page-about .tl-item::before {
    left: calc(var(--about-year-w) + 25px);
    top: 15px;
  }

  .page-about .tl-item::after {
    content: "";
    position: absolute;
    top: 24px;
    bottom: 0;
    left: calc(var(--about-year-w) + 28px);
    width: 1px;
    background: rgba(201, 210, 220, .1);
  }

  .page-about .tl-item:last-child::after { display: none; }

  .page-about .tl-year {
    margin: 0;
    padding-right: 0;
    text-align: right;
    font-size: 39px;
    line-height: 1;
  }

  .page-about .tl-entry {
    align-self: start;
  }
}

@media (min-width: 1280px) {
  .page-about .tl-year { font-size: 49px; }
}

/* ---------- 02 四条业务线（纸面） ---------- */
.page-about .about-lines {
  padding: var(--about-sec) 0;
  background: var(--paper-050);
  color: var(--ink-900);
  border-top: 1px solid rgba(10, 18, 32, .12);
}

.page-about .about-lines .about-sec-head h2 { color: var(--ink-900); }
.page-about .about-lines .eyebrow { color: var(--about-gold-deep); }

.page-about .lines-grid {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 0;
}

.page-about .line-cell {
  padding: 26px 0;
  border-top: 1px solid var(--about-paper-line);
}

.page-about .line-id {
  display: block;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .16em;
  color: var(--about-gold-deep);
  font-variant-numeric: tabular-nums;
}

.page-about .line-name {
  margin: 10px 0 0;
  font-family: var(--font-serif);
  font-weight: 600;
  font-size: 20px;
  line-height: 1.35;
  color: var(--ink-900);
}

.page-about .line-prod {
  margin: 10px 0 0;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .06em;
  color: var(--slate-600);
}

.page-about .line-desc {
  margin: 12px 0 0;
  font-size: 15px;
  line-height: 1.8;
  color: var(--slate-600);
}

.page-about .lines-foot {
  margin: 40px 0 0;
  padding-top: 20px;
  border-top: 1px solid var(--about-paper-line);
  font-size: 14px;
  line-height: 1.8;
  color: var(--slate-600);
}

.page-about .lines-foot a {
  color: var(--ink-900);
  text-decoration: none;
  border-bottom: 1px solid var(--gold-500);
  padding-bottom: 1px;
}

.page-about .lines-foot a:hover,
.page-about .lines-foot a:focus-visible {
  color: var(--about-gold-deep);
  border-bottom-color: var(--about-gold-deep);
}

@media (min-width: 1024px) {
  .page-about .lines-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .line-cell {
    padding: 28px 26px 20px;
  }

  .page-about .line-cell:first-child { padding-left: 0; }
  .page-about .line-cell:last-child { padding-right: 0; }
}

/* ---------- 03 团队与分区联络 ---------- */
.page-about .about-team {
  padding: var(--about-sec) 0;
  background: var(--ink-900);
}

.page-about .team-grid {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .team-cell {
  padding: 24px 0;
  border-top: var(--hair-soft);
}

.page-about .team-cell:last-child {
  border-bottom: var(--hair-soft);
}

.page-about .team-id {
  display: block;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .18em;
  color: var(--gold-500);
  font-variant-numeric: tabular-nums;
}

.page-about .team-cell h3 {
  margin: 12px 0 0;
  font-family: var(--font-serif);
  font-weight: 600;
  font-size: 18px;
  line-height: 1.4;
  color: var(--white);
}

.page-about .team-cell p {
  margin: 10px 0 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--silver-300);
}

.page-about .team-side {
  display: flex;
  gap: 20px;
  margin-top: 32px;
  padding: 24px;
  background: var(--navy-800);
  border: var(--hair-soft);
  border-left: 2px solid var(--gold-500);
  box-shadow: var(--shadow-panel);
}

.page-about .team-side__text { min-width: 0; }

.page-about .team-side h3 {
  margin: 0;
  font-family: var(--font-serif);
  font-weight: 600;
  font-size: 20px;
  line-height: 1.45;
  color: var(--white);
}

.page-about .team-side h3 .mono {
  font-family: var(--font-mono);
  font-size: 24px;
  letter-spacing: 0;
  color: var(--gold-250);
  margin-right: 4px;
  font-variant-numeric: tabular-nums;
}

.page-about .team-side p {
  margin: 12px 0 0;
  max-width: 62ch;
  font-size: 14px;
  line-height: 1.85;
  color: var(--silver-300);
}

.page-about .team-figure {
  margin: 48px 0 0;
}

@media (min-width: 1024px) {
  .page-about .team-grid {
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    border-top: var(--hair-soft);
    border-bottom: var(--hair-soft);
  }

  .page-about .team-cell {
    padding: 28px 26px;
    border-top: 0;
  }

  .page-about .team-cell:last-child { border-bottom: 0; }

  .page-about .team-cell + .team-cell {
    border-left: var(--hair-soft);
  }

  .page-about .team-cell:first-child { padding-left: 0; }
  .page-about .team-cell:last-child { padding-right: 0; }

  .page-about .team-figure { margin-top: 64px; }
}

/* ---------- 04 体系与合规 ---------- */
.page-about .about-systems {
  padding: var(--about-sec) 0;
  background: var(--ink-950);
  border-top: var(--hair-soft);
  border-bottom: var(--hair-soft);
}

.page-about .sys-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 28px;
}

.page-about .sys-item {
  position: relative;
  padding: 24px 0 0;
  border-top: var(--hair-soft);
}

.page-about .sys-head {
  display: flex;
  align-items: center;
  gap: 10px;
}

.page-about .sys-dot {
  flex: 0 0 auto;
  width: 8px;
  height: 8px;
  background: var(--teal-450);
}

.page-about .sys-year {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 14px;
  letter-spacing: .08em;
  color: var(--gold-250);
  font-variant-numeric: tabular-nums;
}

.page-about .sys-item h3 {
  margin: 14px 0 0;
  font-family: var(--font-serif);
  font-weight: 600;
  font-size: 20px;
  line-height: 1.4;
  color: var(--white);
}

.page-about .sys-item p {
  margin: 12px 0 16px;
  max-width: 52ch;
  font-size: 14px;
  line-height: 1.85;
  color: var(--silver-300);
}

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

  .page-about .sys-item {
    padding: 0 32px;
    border-top: 0;
    border-left: var(--hair-soft);
  }

  .page-about .sys-item:first-child {
    padding-left: 0;
    border-left: 0;
  }

  .page-about .sys-item:last-child { padding-right: 0; }
}

/* ---------- 05 长期维护 ---------- */
.page-about .about-upkeep {
  padding: var(--about-sec) 0;
  background: var(--ink-900);
}

.page-about .upkeep-list {
  margin: 0;
  padding: 0;
  display: grid;
  gap: 0;
  border-top: var(--hair-soft);
}

.page-about .upkeep-item {
  display: grid;
  gap: 8px;
  padding: 22px 0;
  border-bottom: var(--hair-soft);
}

.page-about .upkeep-item dt {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .12em;
  color: var(--gold-500);
  font-variant-numeric: tabular-nums;
}

.page-about .upkeep-item dd {
  margin: 0;
  max-width: 64ch;
  font-size: 15px;
  line-height: 1.85;
  color: var(--silver-300);
}

.page-about .upkeep-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin: 40px 0 0;
}

.page-about .upkeep-actions .btn {
  min-height: 44px;
}

@media (min-width: 1024px) {
  .page-about .upkeep-item {
    grid-template-columns: 200px minmax(0, 1fr);
    gap: 32px;
    align-items: baseline;
    padding: 26px 0;
  }

  .page-about .upkeep-actions { margin-top: 56px; }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .tl-entry summary::after,
  .page-about .about-index a,
  .page-about .about-crumb a {
    transition: none;
  }
}