.page-about {
  --about-rail: 244px;
  --about-rule: rgba(29, 62, 92, 0.6);
  --about-gap: 56px;
  display: block;
  padding-bottom: 24px;
}

/* ---------- 顶部上下文条 ---------- */
.page-about .about-topline {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px 20px;
  padding-top: 26px;
  padding-bottom: 4px;
  border-bottom: 1px solid var(--about-rule);
}

.page-about .about-stamp {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--step-11);
  letter-spacing: 0.1em;
  color: var(--muted);
  text-transform: uppercase;
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  display: grid;
  gap: 30px;
  padding-top: 34px;
  padding-bottom: 48px;
}

.page-about .about-hero::before {
  content: "";
  position: absolute;
  inset: 0 -12px 0 -12px;
  background-image:
    linear-gradient(to right, rgba(29, 62, 92, 0.24) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(29, 62, 92, 0.24) 1px, transparent 1px);
  background-size: 72px 72px;
  pointer-events: none;
  z-index: 0;
  -webkit-mask-image: linear-gradient(to bottom, #000 0%, transparent 88%);
  mask-image: linear-gradient(to bottom, #000 0%, transparent 88%);
}

.page-about .about-hero > * {
  position: relative;
  z-index: 1;
}

.page-about .about-label {
  margin: 0 0 14px;
  font-family: var(--font-sans);
  font-size: var(--step-11);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--green);
}

.page-about .about-hero h1 {
  margin: 0 0 20px;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(34px, 7vw, 72px);
  line-height: 1.05;
  letter-spacing: -0.02em;
  color: var(--text);
  text-wrap: balance;
}

.page-about .about-lede {
  margin: 0;
  max-width: 62ch;
  font-family: var(--font-sans);
  font-size: var(--step-17);
  line-height: 1.9;
  color: var(--muted);
}

.page-about .hero-figures {
  list-style: none;
  margin: 30px 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 1px;
  background: var(--about-rule);
  border: 1px solid var(--about-rule);
}

.page-about .hero-figure {
  background: var(--ink-900);
  padding: 14px 12px 16px;
}

.page-about .hero-num {
  display: block;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: clamp(20px, 4.4vw, 26px);
  line-height: 1.1;
  color: var(--amber);
  letter-spacing: -0.01em;
}

.page-about .hero-cap {
  display: block;
  margin-top: 6px;
  font-family: var(--font-sans);
  font-size: var(--step-11);
  letter-spacing: 0.08em;
  color: var(--muted);
}

.page-about .about-hero-media {
  position: relative;
  margin: 0;
  padding: 10px;
  background: var(--ink-800);
  border: 1px solid var(--about-rule);
}

.page-about .about-hero-media::after {
  content: "";
  position: absolute;
  right: -12px;
  bottom: -12px;
  width: 44%;
  height: 34%;
  border-right: 2px solid var(--green);
  border-bottom: 2px solid var(--green);
  pointer-events: none;
}

.page-about .about-hero-media img {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 3 / 2;
  object-fit: cover;
  filter: saturate(0.72) contrast(1.06);
}

.page-about .about-hero-media figcaption {
  margin: 10px 2px 2px;
  font-family: var(--font-sans);
  font-size: var(--step-11);
  line-height: 1.7;
  letter-spacing: 0.04em;
  color: var(--muted);
}

/* ---------- 主体：正文流 + 侧栏索引 ---------- */
.page-about .about-body {
  display: grid;
  gap: 40px;
  padding-top: 8px;
  padding-bottom: 80px;
}

.page-about .about-flow {
  counter-reset: chapter;
  display: grid;
  gap: var(--about-gap);
  min-width: 0;
}

.page-about .about-chapter {
  counter-increment: chapter;
  scroll-margin-top: calc(var(--header-h) + 28px);
  min-width: 0;
}

.page-about .chapter-head {
  padding-bottom: 14px;
  margin-bottom: 24px;
  border-bottom: 1px solid var(--about-rule);
}

.page-about .chapter-num {
  margin: 0 0 8px;
  font-family: var(--font-mono);
  font-size: var(--step-13);
  letter-spacing: 0.16em;
  color: var(--green);
}

.page-about .chapter-num::before {
  content: "CH-" counter(chapter, decimal-leading-zero);
}

.page-about .chapter-title {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(23px, 4.2vw, 34px);
  line-height: 1.24;
  letter-spacing: -0.01em;
  color: var(--text);
  text-wrap: balance;
}

.page-about .para {
  margin: 0 0 18px;
  font-family: var(--font-sans);
  font-size: var(--step-17);
  line-height: 1.9;
  color: var(--text);
  max-width: 68ch;
}

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

.page-about .para--note {
  margin-top: 22px;
  padding-left: 14px;
  border-left: 2px solid var(--green);
  font-size: var(--step-15);
  line-height: 1.85;
  color: var(--muted);
}

/* ---------- 口径切换 ---------- */
.page-about .about-tabs {
  margin: 30px 0 0;
  border: 1px solid var(--about-rule);
  background: rgba(12, 33, 54, 0.6);
}

.page-about .about-tablist {
  display: flex;
  flex-wrap: wrap;
  border-bottom: 1px solid var(--about-rule);
}

.page-about .about-tab {
  appearance: none;
  flex: 1 1 auto;
  min-width: 140px;
  padding: 13px 18px;
  border: 0;
  border-right: 1px solid var(--about-rule);
  background: transparent;
  font-family: var(--font-sans);
  font-size: var(--step-13);
  letter-spacing: 0.12em;
  color: var(--muted);
  cursor: pointer;
  transition: color 0.16s linear, background 0.16s linear, box-shadow 0.16s linear;
}

.page-about .about-tab:last-child {
  border-right: 0;
}

.page-about .about-tab:hover {
  color: var(--text);
  background: rgba(56, 217, 240, 0.07);
}

.page-about .about-tab.is-active {
  color: var(--ink-950);
  background: var(--cyan);
  box-shadow: inset 0 -3px 0 var(--amber);
}

.page-about .about-tab:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: -3px;
}

.page-about .about-tabpanels {
  padding: 20px 18px 22px;
}

.page-about .about-tabpanel[hidden] {
  display: none;
}

.page-about .about-tabpanel .panel-kicker {
  margin: 0 0 10px;
  font-family: var(--font-mono);
  font-size: var(--step-11);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--amber);
}

.page-about .about-tabpanel .para {
  font-size: var(--step-15);
  line-height: 1.85;
}

/* ---------- 信息图与配图 ---------- */
.page-about .about-diagram {
  margin: 28px 0 0;
  padding: 16px 14px 12px;
  border: 1px solid var(--about-rule);
  background: var(--ink-900);
}

.page-about .about-diagram svg {
  display: block;
  width: 100%;
  height: auto;
}

.page-about .about-diagram figcaption,
.page-about .about-figure figcaption {
  margin-top: 12px;
  font-family: var(--font-sans);
  font-size: var(--step-11);
  line-height: 1.7;
  color: var(--muted);
}

.page-about .about-figure {
  margin: 28px 0 0;
}

.page-about .about-figure img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
  border: 1px solid var(--about-rule);
  filter: saturate(0.7) contrast(1.05);
}

/* ---------- 收录门槛 ---------- */
.page-about .threshold-set {
  list-style: none;
  margin: 26px 0 0;
  padding: 0;
  display: grid;
  gap: 18px;
}

.page-about .threshold-card {
  position: relative;
  z-index: 0;
  padding: 20px 18px 22px;
  background: var(--paper);
  color: var(--ink-950);
  border: 1px solid var(--ink-950);
}

.page-about .threshold-card::after {
  content: "";
  position: absolute;
  inset: 8px -8px -8px 8px;
  border: 1px solid var(--line);
  z-index: -1;
  pointer-events: none;
}

.page-about .threshold-idx {
  margin: 0 0 10px;
  font-family: var(--font-mono);
  font-size: var(--step-11);
  letter-spacing: 0.16em;
  color: var(--ink-800);
}

.page-about .threshold-name {
  margin: 0 0 10px;
  font-family: var(--font-display);
  font-size: var(--step-20);
  font-weight: 700;
  line-height: 1.3;
  color: var(--ink-950);
}

.page-about .threshold-text {
  margin: 0;
  font-family: var(--font-sans);
  font-size: var(--step-15);
  line-height: 1.8;
  color: #16283c;
}

/* ---------- 更新流程 ---------- */
.page-about .pipeline {
  list-style: none;
  margin: 26px 0 0;
  padding: 0;
  display: grid;
  gap: 1px;
  background: var(--about-rule);
  border: 1px solid var(--about-rule);
}

.page-about .pipeline-step {
  display: grid;
  grid-template-columns: 42px 1fr;
  grid-template-areas:
    "idx name"
    "idx owner"
    "idx desc";
  gap: 4px 12px;
  padding: 16px 16px 18px;
  background: var(--ink-900);
}

.page-about .pipeline-index {
  grid-area: idx;
  font-family: var(--font-mono);
  font-size: var(--step-13);
  letter-spacing: 0.08em;
  color: var(--amber);
}

.page-about .pipeline-name {
  grid-area: name;
  font-family: var(--font-display);
  font-size: var(--step-20);
  font-weight: 700;
  color: var(--text);
}

.page-about .pipeline-owner {
  grid-area: owner;
  font-family: var(--font-sans);
  font-size: var(--step-11);
  letter-spacing: 0.12em;
  color: var(--green);
}

.page-about .pipeline-desc {
  grid-area: desc;
  margin-top: 4px;
  font-family: var(--font-sans);
  font-size: var(--step-15);
  line-height: 1.8;
  color: var(--muted);
}

.page-about .rhythm-grid {
  display: grid;
  gap: 16px;
  margin-top: 22px;
}

.page-about .rhythm-card {
  padding: 20px 18px 22px;
  border: 1px solid var(--about-rule);
  background: var(--ink-800);
  border-top-width: 3px;
}

.page-about .rhythm-card--match {
  border-top-color: var(--live);
}

.page-about .rhythm-card--idle {
  border-top-color: var(--cyan);
}

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

.page-about .rhythm-value {
  margin: 0 0 12px;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: clamp(22px, 4.6vw, 34px);
  line-height: 1.15;
  color: var(--text);
  letter-spacing: -0.01em;
}

.page-about .rhythm-card--match .rhythm-value {
  color: var(--amber);
}

.page-about .rhythm-note {
  margin: 0;
  font-family: var(--font-sans);
  font-size: var(--step-15);
  line-height: 1.85;
  color: var(--muted);
}

/* ---------- 发展节点（时间线式折叠） ---------- */
.page-about .milestone-list {
  margin-top: 26px;
  border-top: 1px solid var(--about-rule);
}

.page-about .milestone-item {
  border-bottom: 1px solid var(--about-rule);
}

.page-about .milestone-heading {
  margin: 0;
  font-size: inherit;
  font-weight: inherit;
}

.page-about .milestone-list .accordion-trigger {
  display: grid;
  grid-template-columns: 18px 1fr;
  grid-template-areas:
    "node stage"
    "node title";
  gap: 4px 14px;
  width: 100%;
  padding: 20px 16px 20px 10px;
  border: 0;
  border-left: 3px solid transparent;
  background: transparent;
  text-align: left;
  cursor: pointer;
  transition: background 0.16s linear, border-left-color 0.16s linear;
}

.page-about .milestone-list .accordion-trigger:hover {
  background: rgba(56, 217, 240, 0.06);
}

.page-about .milestone-list .accordion-trigger[aria-expanded="true"] {
  border-left-color: var(--amber);
  background: rgba(255, 176, 32, 0.05);
}

.page-about .milestone-list .accordion-trigger:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: -2px;
}

.page-about .milestone-node {
  grid-area: node;
  align-self: center;
  justify-self: center;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--amber);
  box-shadow: 0 0 0 4px rgba(255, 176, 32, 0.16);
}

.page-about .milestone-stage {
  grid-area: stage;
  font-family: var(--font-mono);
  font-size: var(--step-11);
  letter-spacing: 0.16em;
  color: var(--green);
}

.page-about .milestone-title {
  grid-area: title;
  font-family: var(--font-display);
  font-size: var(--step-20);
  font-weight: 700;
  line-height: 1.35;
  color: var(--text);
}

.page-about .milestone-panel {
  padding: 0 16px 22px 42px;
}

.page-about .milestone-panel .para {
  font-size: var(--step-15);
  line-height: 1.85;
  color: var(--muted);
}

/* ---------- 三组分工 ---------- */
.page-about .team-table {
  margin-top: 26px;
  border: 1px solid var(--about-rule);
  overflow-x: auto;
}

.page-about .team-table table {
  width: 100%;
  min-width: 560px;
  border-collapse: collapse;
}

.page-about .team-table caption {
  padding: 12px 14px;
  text-align: left;
  font-family: var(--font-mono);
  font-size: var(--step-11);
  letter-spacing: 0.12em;
  color: var(--muted);
  border-bottom: 1px solid var(--about-rule);
}

.page-about .team-table th,
.page-about .team-table td {
  padding: 13px 14px;
  text-align: left;
  vertical-align: top;
  font-family: var(--font-sans);
  font-size: var(--step-13);
  line-height: 1.7;
  color: var(--text);
  border-bottom: 1px solid var(--about-rule);
}

.page-about .team-table thead th {
  font-family: var(--font-sans);
  font-size: var(--step-11);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
  background: var(--ink-800);
  white-space: nowrap;
}

.page-about .team-table tbody th {
  font-weight: 700;
  color: var(--green);
  white-space: nowrap;
}

.page-about .team-table tbody tr:hover th,
.page-about .team-table tbody tr:hover td {
  background: rgba(56, 217, 240, 0.07);
}

.page-about .team-table tbody tr:last-child th,
.page-about .team-table tbody tr:last-child td {
  border-bottom: 0;
}

/* ---------- 继续查阅 ---------- */
.page-about .about-next {
  padding-top: 30px;
  border-top: 1px solid var(--about-rule);
}

.page-about .next-links {
  display: grid;
  gap: 12px;
}

.page-about .next-link {
  display: grid;
  gap: 6px;
  padding: 16px 18px;
  border: 1px solid var(--about-rule);
  border-left: 3px solid var(--green);
  background: var(--ink-800);
  text-decoration: none;
  transition: border-left-color 0.16s linear, background 0.16s linear, transform 0.16s ease-out;
}

.page-about .next-link:hover,
.page-about .next-link:focus-visible {
  border-left-color: var(--amber);
  background: var(--ink-900);
  transform: translateY(-2px);
}

.page-about .next-link:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 2px;
}

.page-about .next-link-title {
  font-family: var(--font-display);
  font-size: var(--step-20);
  font-weight: 700;
  color: var(--text);
}

.page-about .next-link-note {
  font-family: var(--font-sans);
  font-size: var(--step-13);
  line-height: 1.7;
  color: var(--muted);
}

/* ---------- 侧栏索引 ---------- */
.page-about .about-index {
  padding-top: 16px;
  border-top: 2px solid var(--green);
  min-width: 0;
}

.page-about .index-title {
  margin: 0 0 14px;
  font-family: var(--font-mono);
  font-size: var(--step-11);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--muted);
}

.page-about .index-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 2px;
}

.page-about .index-link {
  display: grid;
  grid-template-columns: 30px 1fr;
  gap: 10px;
  align-items: baseline;
  padding: 9px 8px;
  border-left: 2px solid transparent;
  font-family: var(--font-sans);
  font-size: var(--step-13);
  line-height: 1.6;
  color: var(--muted);
  text-decoration: none;
  transition: color 0.16s linear, border-left-color 0.16s linear, background 0.16s linear;
}

.page-about .index-link:hover,
.page-about .index-link:focus-visible {
  color: var(--text);
  border-left-color: var(--amber);
  background: rgba(255, 176, 32, 0.07);
}

.page-about .index-link:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 1px;
}

.page-about .index-num {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: var(--step-11);
  letter-spacing: 0.08em;
  color: var(--green);
}

.page-about .index-footnote {
  margin: 18px 0 0;
  padding-top: 14px;
  border-top: 1px solid var(--about-rule);
  font-family: var(--font-sans);
  font-size: var(--step-11);
  line-height: 1.8;
  color: var(--muted);
}

/* ---------- 响应式 ---------- */
@media (min-width: 640px) {
  .page-about .threshold-set {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .page-about .pipeline-step {
    grid-template-columns: 52px minmax(120px, 180px) minmax(0, 1fr);
    grid-template-areas:
      "idx name desc"
      "idx owner desc";
    align-items: start;
    padding: 18px 20px;
  }

  .page-about .pipeline-owner {
    margin-top: 4px;
  }

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

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

@media (min-width: 900px) {
  .page-about .about-hero {
    grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
    align-items: end;
    gap: 48px;
    padding-top: 44px;
    padding-bottom: 68px;
  }

  .page-about .about-hero h1 {
    margin-bottom: 24px;
  }
}

@media (min-width: 1000px) {
  .page-about .about-body {
    grid-template-columns: minmax(0, 1fr) var(--about-rail);
    gap: 60px;
    align-items: start;
  }

  .page-about .about-index {
    position: sticky;
    top: calc(var(--header-h) + 24px);
    max-height: calc(100vh - var(--header-h) - 48px);
    overflow-y: auto;
  }

  .page-about .about-flow {
    --about-gap: 72px;
  }
}

@media (min-width: 1240px) {
  .page-about {
    --about-rail: 268px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .next-link,
  .page-about .about-tab,
  .page-about .index-link,
  .page-about .milestone-list .accordion-trigger {
    transition: none;
  }

  .page-about .next-link:hover {
    transform: none;
  }
}