.page-about {
  --rail-w: 236px;
  --ab-gap: 56px;
  --ab-ink-soft: rgba(242, 245, 244, 0.78);
  padding-bottom: 104px;
}

/* 面包屑 */
.page-about .breadcrumb {
  margin: 26px 0 0;
}

/* 首屏 */
.page-about .about-hero {
  display: grid;
  gap: 30px;
  padding: 26px 0 48px;
  border-bottom: 1px solid var(--line);
}

.page-about .about-hero h1 {
  margin: 12px 0 20px;
  font-size: clamp(32px, 7.4vw, 62px);
  line-height: 1.03;
  letter-spacing: -0.02em;
  font-weight: 800;
  color: var(--paper);
}

.page-about .about-hero .lead {
  margin: 0;
  max-width: 62ch;
  font-size: 16px;
  line-height: 1.75;
  color: var(--ab-ink-soft);
}

.page-about .about-hero-media {
  margin: 0;
  border: 1px solid var(--line);
  background: var(--night);
  overflow: hidden;
}

.page-about .media-frame img {
  display: block;
  width: 100%;
  height: auto;
  max-width: 100%;
  object-fit: cover;
  filter: saturate(0.72) contrast(1.04);
}

/* 快速数据 */
.page-about .about-quickstats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 28px 0 0;
  padding: 1px;
  list-style: none;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .about-quickstats li {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 14px 16px;
  background: var(--ink);
}

.page-about .qs-num {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 26px;
  line-height: 1;
  color: var(--cyan);
  letter-spacing: -0.02em;
}

.page-about .qs-label {
  font-size: 12px;
  letter-spacing: 0.04em;
  color: var(--muted);
}

/* 主体走廊 */
.page-about .about-body {
  display: grid;
  gap: 36px;
  padding-top: 48px;
}

/* 侧栏 */
.page-about .about-rail {
  display: none;
}

.page-about .rail-block {
  padding: 0 0 20px;
  margin-bottom: 20px;
  border-bottom: 1px solid var(--line);
}

.page-about .rail-label {
  margin: 0 0 10px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
}

.page-about .rail-total {
  display: flex;
  align-items: baseline;
  gap: 6px;
  margin: 0 0 6px;
}

.page-about .rail-total .numeral-xl {
  font-size: 54px;
  line-height: 0.9;
  color: var(--orange);
}

.page-about .rail-unit {
  font-size: 13px;
  color: var(--muted);
}

.page-about .rail-note {
  margin: 0;
  font-size: 12px;
  line-height: 1.6;
  color: var(--muted);
}

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

.page-about .rail-list li {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 10px;
  padding: 7px 0;
  font-size: 13px;
  color: var(--ab-ink-soft);
  border-bottom: 1px dashed var(--line);
}

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

.page-about .rail-v {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  color: var(--paper);
}

.page-about .rail-nav ul {
  margin: 0;
  padding: 0;
  list-style: none;
}

.page-about .rail-nav li {
  margin-bottom: 2px;
}

.page-about .rail-nav a {
  display: flex;
  gap: 10px;
  padding: 7px 0;
  font-size: 13px;
  color: var(--muted);
  text-decoration: none;
  border-left: 2px solid transparent;
  padding-left: 10px;
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}

.page-about .rail-nav a span {
  font-family: var(--font-mono);
  color: var(--line);
  transition: color var(--dur) var(--ease);
}

.page-about .rail-nav a:hover,
.page-about .rail-nav a:focus-visible {
  color: var(--paper);
  border-left-color: var(--orange);
}

.page-about .rail-nav a:hover span,
.page-about .rail-nav a:focus-visible span {
  color: var(--orange);
}

/* 章节 */
.page-about .about-chapter {
  padding-top: 36px;
  margin-bottom: 64px;
}

.page-about .about-chapter--last {
  margin-bottom: 0;
}

.page-about .about-chapter-head {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 6px 16px;
  align-items: start;
  margin-bottom: 26px;
}

.page-about .about-chapter-head .chapter-index {
  padding-top: 4px;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 13px;
  letter-spacing: 0.1em;
  color: var(--orange);
}

.page-about .about-chapter-head .eyebrow {
  margin: 0 0 8px;
}

.page-about .about-chapter-head .section-title {
  margin: 0;
  font-size: clamp(22px, 4.4vw, 34px);
  line-height: 1.16;
  letter-spacing: -0.01em;
  color: var(--paper);
}

.page-about .about-text p {
  margin: 0 0 16px;
  font-size: 15.5px;
  line-height: 1.78;
  color: var(--ab-ink-soft);
  max-width: 68ch;
}

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

/* 分工比例条 */
.page-about .ratio-block {
  margin-top: 28px;
  padding: 20px;
  border: 1px solid var(--line);
  background: var(--night);
}

.page-about .ratio-title {
  margin: 0 0 14px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
}

.page-about .ratio-bar {
  display: flex;
  height: 16px;
  border: 1px solid var(--line);
  background: var(--ink);
}

.page-about .ratio-seg {
  display: block;
  height: 100%;
  transition: opacity var(--dur) var(--ease);
}

.page-about .ratio-seg--edit {
  width: 50%;
  background: var(--orange);
}

.page-about .ratio-seg--ver {
  width: 22.22%;
  background: var(--cyan);
}

.page-about .ratio-seg--ops {
  width: 27.78%;
  background: var(--muted);
}

.page-about .ratio-bar:hover .ratio-seg {
  opacity: 0.78;
}

.page-about .ratio-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 22px;
  margin: 14px 0 0;
  padding: 0;
  list-style: none;
}

.page-about .ratio-legend li {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 12.5px;
  color: var(--muted);
}

.page-about .dot {
  display: inline-block;
  width: 10px;
  height: 10px;
  flex: 0 0 auto;
}

.page-about .dot--edit {
  background: var(--orange);
}

.page-about .dot--ver {
  background: var(--cyan);
}

.page-about .dot--ops {
  background: var(--muted);
}

/* 流水线步骤 */
.page-about .steps {
  margin: 24px 0 0;
  padding: 1px;
  list-style: none;
  display: grid;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .step {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 14px;
  padding: 18px;
  background: var(--night);
  transition: background var(--dur) var(--ease);
}

.page-about .step:hover,
.page-about .step:focus-within {
  background: var(--panel);
}

.page-about .step-n {
  padding-top: 3px;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--orange);
}

.page-about .step h3 {
  margin: 0 0 6px;
  font-size: 16px;
  line-height: 1.35;
  color: var(--paper);
}

.page-about .step p {
  margin: 0;
  font-size: 14px;
  line-height: 1.72;
  color: var(--muted);
}

/* 图片 */
.page-about .about-figure {
  margin: 28px 0 0;
  border: 1px solid var(--line);
  background: var(--night);
  overflow: hidden;
}

.page-about .about-figure figcaption {
  padding: 10px 14px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.04em;
  color: var(--muted);
  border-top: 1px solid var(--line);
}

/* 版本面板 */
.page-about .version-panel {
  margin: 26px 0 0;
  padding: 20px;
  border: 1px solid var(--line);
  background: var(--night);
}

.page-about .vp-label {
  margin: 0 0 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
}

.page-about .vp-code {
  margin: 0 0 18px;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: clamp(30px, 7vw, 46px);
  line-height: 1;
  letter-spacing: 0.04em;
  color: var(--cyan);
}

.page-about .vp-parts {
  display: grid;
  gap: 14px;
  margin: 0;
  padding-top: 16px;
  border-top: 1px solid var(--line);
}

.page-about .vp-parts dt {
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--paper);
  margin-bottom: 3px;
}

.page-about .vp-parts dd {
  margin: 0;
  font-size: 13px;
  line-height: 1.66;
  color: var(--muted);
}

.page-about .version-points {
  margin: 22px 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .version-points li {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  padding: 13px 16px;
  background: var(--ink);
  font-size: 14px;
  line-height: 1.6;
  color: var(--ab-ink-soft);
}

/* 阶段卡 */
.page-about .history-grid {
  display: grid;
  gap: 14px;
  margin: 24px 0 0;
  padding: 0;
  list-style: none;
}

.page-about .stage {
  position: relative;
  padding: 18px;
  border: 1px solid var(--line);
  background: var(--ink);
  transition: border-color var(--dur) var(--ease), background var(--dur) var(--ease);
}

.page-about .stage::before {
  content: "";
  position: absolute;
  top: -1px;
  left: 0;
  width: 30px;
  height: 2px;
  background: var(--orange);
}

.page-about .stage:hover,
.page-about .stage:focus-within {
  border-color: var(--orange);
  background: rgba(255, 90, 31, 0.06);
}

.page-about .stage-num {
  display: block;
  margin-bottom: 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--orange);
}

.page-about .stage h3 {
  margin: 0 0 8px;
  font-size: 16px;
  line-height: 1.35;
  color: var(--paper);
}

.page-about .stage p {
  margin: 0;
  font-size: 13.5px;
  line-height: 1.72;
  color: var(--muted);
}

/* 规范条目 */
.page-about .spec-list {
  margin-top: 24px;
  border-top: 1px solid var(--line);
}

.page-about .spec-list details {
  border-bottom: 1px solid var(--line);
}

.page-about .spec-list summary {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  padding: 16px 0;
  cursor: pointer;
  list-style: none;
  font-size: 15px;
  font-weight: 600;
  color: var(--paper);
  transition: color var(--dur) var(--ease);
}

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

.page-about .spec-list summary::after {
  content: "+";
  font-family: var(--font-mono);
  font-size: 18px;
  line-height: 1;
  color: var(--orange);
}

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

.page-about .spec-list summary:hover,
.page-about .spec-list summary:focus-visible {
  color: var(--orange);
}

.page-about .spec-list details p {
  margin: 0 0 18px;
  padding-right: 28px;
  font-size: 14px;
  line-height: 1.76;
  color: var(--muted);
  max-width: 66ch;
}

/* 后续入口 */
.page-about .next-grid {
  display: grid;
  gap: 1px;
  margin-top: 24px;
  padding: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .next-card {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 4px 12px;
  padding: 20px;
  background: var(--night);
  text-decoration: none;
  transition: background var(--dur) var(--ease);
}

.page-about .next-card:hover,
.page-about .next-card:focus-visible {
  background: var(--panel);
}

.page-about .next-kicker {
  grid-column: 1;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--orange);
}

.page-about .next-title {
  grid-column: 1;
  font-size: 15px;
  line-height: 1.6;
  color: var(--paper);
}

.page-about .next-arrow {
  grid-column: 2;
  grid-row: 1 / span 2;
  align-self: center;
  font-family: var(--font-mono);
  font-size: 18px;
  color: var(--muted);
  transition: color var(--dur) var(--ease), transform var(--dur) var(--ease);
}

.page-about .next-card:hover .next-arrow,
.page-about .next-card:focus-visible .next-arrow {
  color: var(--cyan);
}

/* 响应式 */
@media (min-width: 600px) {
  .page-about .about-quickstats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

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

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

@media (min-width: 760px) {
  .page-about .next-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .page-about .step {
    grid-template-columns: 48px minmax(0, 1fr);
    padding: 20px 22px;
  }
}

@media (min-width: 900px) {
  .page-about {
    padding-bottom: 128px;
  }

  .page-about .about-hero {
    grid-template-columns: minmax(0, 1.05fr) minmax(0, 0.95fr);
    align-items: end;
    gap: 48px;
    padding: 30px 0 56px;
  }

  .page-about .about-body {
    grid-template-columns: var(--rail-w) minmax(0, 1fr);
    gap: var(--ab-gap);
    padding-top: 56px;
  }

  .page-about .about-rail {
    display: block;
    position: sticky;
    top: calc(var(--header-h) + 24px);
    align-self: start;
  }

  .page-about .about-chapter-head {
    gap: 8px 22px;
  }

  .page-about .about-text p {
    font-size: 16px;
  }
}

@media (min-width: 1100px) {
  .page-about .history-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .next-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .step,
  .page-about .stage,
  .page-about .next-card,
  .page-about .next-arrow,
  .page-about .ratio-seg,
  .page-about .rail-nav a,
  .page-about .spec-list summary {
    transition: none;
  }
}
<<<END>>>