.page-about {
  --about-toc-w: 232px;
  --about-line: var(--edge);
  background: var(--ink-900);
  color: var(--text-dark);
  font-family: var(--font-body);
  padding-bottom: clamp(40px, 6vw, 84px);
}

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

/* ---------- 面包屑 ---------- */
.page-about .breadcrumb {
  padding: 18px 0 0;
  font-size: 13px;
  color: var(--index);
}

.page-about .breadcrumb a {
  color: var(--text-mute);
  text-decoration: none;
  border-bottom: 1px solid transparent;
}

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

.page-about .breadcrumb span[aria-current="page"] {
  color: var(--gold);
  font-family: var(--font-mono);
  letter-spacing: 0.08em;
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  padding: clamp(28px, 5vw, 54px) 0 clamp(34px, 5vw, 64px);
  border-bottom: var(--bw) solid var(--edge-soft);
}

.page-about .hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(26px, 4vw, 44px);
  align-items: center;
}

.page-about .hero-copy .kicker {
  display: inline-block;
  margin: 0 0 16px;
  padding: 4px 10px;
  border: var(--bw) solid var(--edge);
  color: var(--cyan);
  font-size: 12px;
  letter-spacing: 0.14em;
}

.page-about h1 {
  margin: 0 0 18px;
  font-family: var(--font-display);
  font-size: clamp(29px, 5vw, 44px);
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -0.02em;
  color: var(--paper);
}

.page-about .hero-lede {
  margin: 0;
  max-width: 60ch;
  font-size: clamp(15px, 1.6vw, 17px);
  line-height: 1.85;
  color: var(--text-mute);
}

.page-about .hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 26px;
}

.page-about .hero-figure {
  margin: 0;
  border: var(--bw) solid var(--edge);
  box-shadow: var(--shadow-hard-cyan);
  background: linear-gradient(140deg, var(--band-teal), var(--band-wine));
  overflow: hidden;
}

.page-about .hero-figure img {
  width: 100%;
  object-fit: cover;
}

.page-about .hero-stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: clamp(28px, 4vw, 46px) 0 0;
  padding: 0;
  list-style: none;
  background: var(--edge-soft);
  border: var(--bw) solid var(--edge);
}

.page-about .hero-stats li {
  background: var(--ink-800);
  padding: 16px 18px;
}

.page-about .stat-v {
  display: block;
  font-size: clamp(20px, 2.6vw, 26px);
  line-height: 1.2;
  color: var(--gold);
}

.page-about .stat-k {
  display: block;
  margin-top: 6px;
  font-size: 13px;
  color: var(--index);
}

/* ---------- 长卷布局与左侧索引 ---------- */
.page-about .about-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(24px, 3.5vw, 44px);
  padding-top: clamp(34px, 5vw, 62px);
}

.page-about .about-toc-title {
  margin: 0 0 12px;
  font-size: 11px;
  letter-spacing: 0.2em;
  color: var(--index);
}

.page-about .chapter-nav ul {
  display: flex;
  gap: 8px;
  margin: 0;
  padding: 0 0 6px;
  list-style: none;
  overflow-x: auto;
}

.page-about .chapter-link {
  display: flex;
  align-items: baseline;
  gap: 9px;
  padding: 9px 12px;
  font-size: 14px;
  color: var(--text-mute);
  text-decoration: none;
  background: var(--ink-800);
  border: var(--bw) solid var(--edge-soft);
  white-space: nowrap;
  transition: color 0.18s ease, border-color 0.18s ease, background 0.18s ease;
}

.page-about .chapter-link .mono {
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--index);
}

.page-about .chapter-link:hover,
.page-about .chapter-link:focus-visible {
  color: var(--cyan);
  border-color: var(--cyan);
}

.page-about .chapter-link[aria-current="true"] {
  color: var(--gold);
  border-color: var(--gold);
  background: rgba(242, 180, 65, 0.08);
}

.page-about .chapter-link[aria-current="true"] .mono {
  color: var(--gold);
}

/* ---------- 章节与色带 ---------- */
.page-about .about-sec {
  padding-bottom: clamp(42px, 6vw, 78px);
  scroll-margin-top: 96px;
}

.page-about .chapter-band {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: clamp(12px, 2vw, 20px);
  margin: 0 0 clamp(20px, 3vw, 30px);
  padding: 14px clamp(14px, 2.4vw, 22px);
  border: var(--bw) solid var(--edge);
  border-left: 6px solid var(--cyan);
  background: linear-gradient(100deg, rgba(14, 59, 62, 0.92) 0%, rgba(23, 28, 74, 0.78) 60%, rgba(11, 16, 48, 0.45) 100%);
}

.page-about .chapter-band[data-tone="wine"] {
  border-left-color: var(--gold);
  background: linear-gradient(100deg, rgba(74, 22, 51, 0.94) 0%, rgba(23, 28, 74, 0.78) 60%, rgba(11, 16, 48, 0.45) 100%);
}

.page-about .chapter-index {
  font-size: 13px;
  letter-spacing: 0.18em;
  color: var(--gold);
}

.page-about .chapter-band[data-tone="wine"] .chapter-index {
  color: var(--cyan);
}

.page-about .chapter-title {
  margin: 0;
  font-family: var(--font-display);
  font-size: clamp(19px, 2.6vw, 26px);
  font-weight: 800;
  letter-spacing: -0.01em;
  color: var(--paper);
}

.page-about .sec-lede {
  margin: 0 0 clamp(18px, 2.6vw, 26px);
  max-width: 64ch;
  font-size: 15.5px;
  line-height: 1.85;
  color: var(--text-mute);
}

/* ---------- 正文与旁注 ---------- */
.page-about .about-split {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(20px, 3vw, 32px);
}

.page-about .about-body p {
  margin: 0 0 16px;
  font-size: 16px;
  line-height: 1.85;
  color: var(--text-dark);
}

.page-about .about-body h3 {
  margin: 26px 0 12px;
  font-family: var(--font-display);
  font-size: clamp(17px, 1.9vw, 20px);
  font-weight: 700;
  color: var(--paper);
}

.page-about .about-body ul {
  margin: 0 0 16px;
  padding: 0;
  list-style: none;
}

.page-about .about-body ul li {
  position: relative;
  margin-bottom: 10px;
  padding-left: 20px;
  font-size: 15.5px;
  line-height: 1.8;
  color: var(--text-mute);
}

.page-about .about-body ul li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.7em;
  width: 8px;
  height: 8px;
  background: var(--cyan);
}

.page-about .about-facts {
  padding: 20px;
  background: var(--ink-800);
  border: var(--bw) solid var(--edge);
  border-top: 6px solid var(--gold);
  box-shadow: var(--shadow-hard-cyan);
  align-self: start;
}

.page-about .facts-title {
  margin: 0 0 12px;
  font-size: 11px;
  letter-spacing: 0.2em;
  color: var(--index);
}

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

.page-about .facts-list li {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 14px;
  padding: 11px 0;
  border-bottom: 1px dashed var(--edge);
  font-size: 14px;
}

.page-about .facts-list li:last-child {
  border-bottom: 0;
  padding-bottom: 0;
}

.page-about .f-k {
  color: var(--index);
}

.page-about .f-v {
  font-family: var(--font-mono);
  letter-spacing: 0.04em;
  color: var(--gold);
  text-align: right;
}

/* ---------- 阅读顺序 ---------- */
.page-about .read-steps {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 14px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.page-about .read-step {
  padding: 20px 18px 18px;
  background: var(--ink-800);
  border: var(--bw) solid var(--edge);
  border-bottom: 6px solid var(--cyan);
}

.page-about .read-step:nth-child(2) {
  border-bottom-color: var(--gold);
}

.page-about .read-step:nth-child(3) {
  border-bottom-color: var(--coral);
}

.page-about .step-idx {
  display: inline-block;
  margin-bottom: 14px;
  padding: 3px 9px;
  border: var(--bw) solid var(--edge);
  font-size: 11px;
  letter-spacing: 0.16em;
  color: var(--cyan);
}

.page-about .read-step h3 {
  margin: 0 0 8px;
  font-family: var(--font-display);
  font-size: 17px;
  font-weight: 700;
  color: var(--paper);
}

.page-about .read-step p {
  margin: 0;
  font-size: 14.5px;
  line-height: 1.78;
  color: var(--text-mute);
}

/* ---------- 里程碑 ---------- */
.page-about .milestone-wrap {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(20px, 3vw, 34px);
}

.page-about .milestone-figure {
  margin: 0;
  border: var(--bw) solid var(--edge);
  background: linear-gradient(160deg, var(--band-wine), var(--band-teal));
  overflow: hidden;
}

.page-about .timeline {
  margin: 0;
  padding: 0 0 0 26px;
  list-style: none;
  border-left: var(--bw) solid var(--edge);
}

.page-about .timeline > li {
  position: relative;
  margin-bottom: 12px;
}

.page-about .timeline > li::before {
  content: "";
  position: absolute;
  left: -34px;
  top: 16px;
  width: 14px;
  height: 14px;
  background: var(--ink-900);
  border: var(--bw) solid var(--cyan);
}

.page-about .ms-item {
  border: var(--bw) solid var(--edge);
  background: var(--ink-800);
}

.page-about .ms-item > summary {
  display: flex;
  align-items: baseline;
  gap: 14px;
  padding: 13px 16px;
  cursor: pointer;
  list-style: none;
  font-family: var(--font-display);
  font-size: 16px;
  font-weight: 700;
  color: var(--paper);
}

.page-about .ms-item > summary::-webkit-details-marker {
  display: none;
}

.page-about .ms-item > summary::after {
  content: "+";
  margin-left: auto;
  font-family: var(--font-mono);
  font-size: 17px;
  color: var(--cyan);
}

.page-about .ms-item[open] > summary::after {
  content: "−";
  color: var(--gold);
}

.page-about .ms-item[open] > summary {
  border-bottom: 1px solid var(--edge-soft);
}

.page-about .ms-year {
  font-size: 13px;
  letter-spacing: 0.12em;
  color: var(--gold);
}

.page-about .ms-body {
  padding: 14px 16px 18px;
  font-size: 14.8px;
  line-height: 1.8;
  color: var(--text-mute);
}

/* ---------- 使用规范 ---------- */
.page-about .rule-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 14px;
}

.page-about .rule-card {
  padding: 18px;
  background: var(--ink-800);
  border: var(--bw) solid var(--edge);
  border-top: 5px solid var(--cyan);
}

.page-about .rule-card:nth-child(3n + 2) {
  border-top-color: var(--gold);
}

.page-about .rule-card:nth-child(3n + 3) {
  border-top-color: var(--coral);
}

.page-about .rule-card h3 {
  margin: 0 0 8px;
  font-family: var(--font-display);
  font-size: 16.5px;
  font-weight: 700;
  color: var(--paper);
}

.page-about .rule-card p {
  margin: 0;
  font-size: 14.5px;
  line-height: 1.78;
  color: var(--text-mute);
}

/* ---------- 雾纸白反转章节 ---------- */
.page-about .about-sec--paper {
  padding: clamp(22px, 3.4vw, 36px);
  background: var(--paper);
  color: var(--slate);
  border: var(--bw) solid var(--slate);
  box-shadow: 10px 10px 0 rgba(53, 230, 208, 0.22);
}

.page-about .about-sec--paper .chapter-band {
  background: rgba(42, 48, 80, 0.08);
  border-color: var(--edge-soft);
  border-left-color: var(--slate);
}

.page-about .about-sec--paper .chapter-index {
  color: var(--slate);
}

.page-about .about-sec--paper .chapter-title {
  color: var(--slate);
}

.page-about .about-sec--paper .sec-lede {
  color: #4A5075;
}

.page-about .cert-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 12px;
}

.page-about .cert-item {
  padding: 16px;
  background: #FFFFFF;
  border: var(--bw) solid var(--slate);
  border-left: 6px solid var(--gold);
}

.page-about .cert-item h3 {
  margin: 0 0 7px;
  font-family: var(--font-display);
  font-size: 16px;
  font-weight: 700;
  color: var(--slate);
}

.page-about .cert-item p {
  margin: 0;
  font-size: 14.5px;
  line-height: 1.78;
  color: #4A5075;
}

/* ---------- 服务区域 ---------- */
.page-about .reach-wrap {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(20px, 3vw, 32px);
  align-items: start;
}

.page-about .reach-list {
  display: grid;
  gap: 10px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.page-about .reach-item {
  padding: 14px 16px;
  background: var(--ink-800);
  border: var(--bw) solid var(--edge);
  transition: border-color 0.18s ease, background 0.18s ease;
}

.page-about .reach-item:hover,
.page-about .reach-item:focus-within {
  border-color: var(--cyan);
  background: rgba(53, 230, 208, 0.07);
}

.page-about .reach-idx {
  display: inline-block;
  font-size: 11px;
  letter-spacing: 0.16em;
  color: var(--gold);
}

.page-about .reach-item h3 {
  margin: 7px 0 5px;
  font-family: var(--font-display);
  font-size: 16px;
  font-weight: 700;
  color: var(--paper);
}

.page-about .reach-item p {
  margin: 0;
  font-size: 14px;
  line-height: 1.72;
  color: var(--text-mute);
}

.page-about .reach-figure {
  margin: 0;
  border: var(--bw) solid var(--edge);
  box-shadow: var(--shadow-hard-cyan);
  background: linear-gradient(120deg, var(--band-teal), var(--band-wine));
  overflow: hidden;
}

.page-about .coop-note {
  margin-top: clamp(22px, 3vw, 34px);
  padding: clamp(18px, 2.6vw, 24px);
  border: var(--bw) solid var(--edge);
  border-left: 6px solid var(--gold);
  background: rgba(23, 28, 74, 0.72);
}

.page-about .coop-note h3 {
  margin-top: 0;
}

/* ---------- 收尾引导 ---------- */
.page-about .about-cta {
  margin-top: clamp(34px, 5vw, 58px);
  padding: clamp(24px, 3.4vw, 40px);
  border: var(--bw) solid var(--edge);
  border-left: 6px solid var(--gold);
  background: linear-gradient(120deg, rgba(23, 28, 74, 0.92), rgba(74, 22, 51, 0.55));
  box-shadow: var(--shadow-hard-cyan);
}

.page-about .about-cta h2 {
  margin: 0 0 10px;
  font-family: var(--font-display);
  font-size: clamp(20px, 2.6vw, 26px);
  font-weight: 800;
  letter-spacing: -0.01em;
  color: var(--paper);
}

.page-about .about-cta p {
  margin: 0 0 20px;
  max-width: 62ch;
  font-size: 15.5px;
  line-height: 1.8;
  color: var(--text-mute);
}

.page-about .about-cta-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

/* ---------- 桌面端 ---------- */
@media (min-width: 780px) {
  .page-about .hero-stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .about-split {
    grid-template-columns: minmax(0, 1.7fr) minmax(0, 1fr);
    gap: clamp(24px, 3.4vw, 40px);
  }

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

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

@media (min-width: 900px) {
  .page-about .hero-grid {
    grid-template-columns: minmax(0, 6.4fr) minmax(0, 5.6fr);
    gap: clamp(32px, 5vw, 64px);
  }

  .page-about .read-steps {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .page-about .milestone-wrap {
    grid-template-columns: minmax(0, 4fr) minmax(0, 7fr);
    align-items: start;
  }

  .page-about .reach-wrap {
    grid-template-columns: minmax(0, 1fr) minmax(0, 1.12fr);
  }
}

@media (min-width: 1024px) {
  .page-about .about-layout {
    grid-template-columns: var(--about-toc-w) minmax(0, 1fr);
    gap: clamp(36px, 4.5vw, 72px);
    align-items: start;
  }

  .page-about .about-toc {
    position: sticky;
    top: 88px;
    align-self: start;
  }

  .page-about .chapter-nav ul {
    flex-direction: column;
    gap: 0;
    overflow: visible;
    padding-bottom: 0;
  }

  .page-about .chapter-link {
    border-width: 0 0 0 3px;
    border-style: solid;
    border-color: transparent;
    background: transparent;
    white-space: normal;
    padding: 10px 0 10px 14px;
  }

  .page-about .chapter-link:hover,
  .page-about .chapter-link:focus-visible {
    border-color: var(--cyan);
    background: rgba(53, 230, 208, 0.06);
  }

  .page-about .chapter-link[aria-current="true"] {
    border-color: var(--gold);
    background: rgba(242, 180, 65, 0.08);
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .chapter-link,
  .page-about .reach-item {
    transition: none;
  }
}