.page-about {
  --about-line: rgba(36, 64, 106, .72);
  --about-line-soft: rgba(36, 64, 106, .46);
  --about-panel: var(--panel-2);
  --about-glow: rgba(47, 240, 214, .12);
  --about-amber-glow: rgba(255, 154, 60, .14);
  padding-bottom: 3.5rem;
}

/* ---------- 面包屑与首屏 ---------- */

.page-about > .breadcrumb {
  margin-top: 1.4rem;
}

.page-about .about-hero {
  padding: 1.6rem 0 2.2rem;
  border-bottom: 1px solid var(--about-line-soft);
}

.page-about .hero-kicker {
  display: inline-flex;
  align-items: center;
  gap: .55rem;
  margin: 0 0 1rem;
  font-family: var(--font-mono);
  font-size: .72rem;
  letter-spacing: .16em;
  color: var(--cyan);
  text-transform: uppercase;
}

.page-about .hero-kicker::before {
  content: "";
  width: 26px;
  height: 2px;
  background: var(--cyan);
  border-radius: 2px;
}

.page-about .about-hero h1 {
  margin: 0 0 1rem;
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 6.4vw, 2.7rem);
  font-weight: 900;
  line-height: 1.32;
  letter-spacing: -.01em;
  color: var(--text);
  max-width: 22ch;
}

.page-about .hero-lede {
  margin: 0;
  max-width: 62ch;
  font-size: .97rem;
  line-height: 1.85;
  color: var(--muted);
}

.page-about .hero-stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: .85rem;
  margin: 1.8rem 0 0;
  padding: 0;
  list-style: none;
}

.page-about .hero-stats .stat {
  padding: .85rem 1rem;
  background: var(--about-panel);
  border: 1px solid var(--about-line-soft);
  border-left: 2px solid var(--cyan);
  border-radius: var(--radius-b);
}

.page-about .hero-stats .stat-value {
  display: block;
  font-family: var(--font-mono);
  font-size: 1.45rem;
  font-weight: 700;
  line-height: 1.1;
  color: var(--amber);
  letter-spacing: -.02em;
}

.page-about .hero-stats .stat-label {
  display: block;
  margin-top: .3rem;
  font-size: .78rem;
  letter-spacing: .04em;
  color: var(--muted);
}

/* ---------- 封面 ---------- */

.page-about .cover-frame {
  position: relative;
  margin: 2.2rem 0 0;
  border: 1px solid var(--about-line);
  border-radius: var(--radius-c);
  overflow: hidden;
  background: var(--about-panel);
}

.page-about .cover-frame img {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 16 / 9;
  object-fit: cover;
}

.page-about .cover-frame figcaption {
  position: absolute;
  left: .9rem;
  bottom: .9rem;
  padding: .3rem .8rem;
  font-family: var(--font-mono);
  font-size: .68rem;
  letter-spacing: .12em;
  color: var(--muted);
  background: rgba(5, 11, 24, .78);
  border: 1px solid var(--about-line);
  border-radius: 999px;
}

/* ---------- 章节导航 ---------- */

.page-about .chapter-nav {
  position: sticky;
  top: 0;
  z-index: 6;
  margin: 1.6rem 0 0;
  padding: .7rem 0 .6rem;
  background: linear-gradient(to bottom, var(--deep) 68%, rgba(5, 11, 24, 0));
}

.page-about .chapter-nav ol {
  display: flex;
  gap: .45rem;
  margin: 0;
  padding: 0 0 .25rem;
  list-style: none;
  overflow-x: auto;
  scrollbar-width: none;
}

.page-about .chapter-nav ol::-webkit-scrollbar {
  display: none;
}

.page-about .chapter-nav a {
  display: inline-block;
  white-space: nowrap;
  padding: .42rem .88rem;
  font-family: var(--font-mono);
  font-size: .75rem;
  letter-spacing: .04em;
  color: var(--muted);
  text-decoration: none;
  border: 1px solid var(--about-line);
  border-radius: 999px;
  transition: color .24s var(--ease), border-color .24s var(--ease), background-color .24s var(--ease);
}

.page-about .chapter-nav a:hover,
.page-about .chapter-nav a:focus-visible {
  color: var(--cyan);
  border-color: var(--cyan-deep);
  background: rgba(15, 185, 166, .1);
}

/* ---------- 章节结构 ---------- */

.page-about .chapter {
  padding: 2.4rem 0 1.6rem;
  scroll-margin-top: 4.5rem;
}

.page-about .chapter-head {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: .55rem 1rem;
  align-items: start;
  margin-bottom: 1.7rem;
}

.page-about .chapter-num {
  font-family: var(--font-mono);
  font-size: clamp(2rem, 9vw, 3.1rem);
  font-weight: 700;
  line-height: .88;
  letter-spacing: -.05em;
  color: var(--grid);
}

.page-about .chapter-title {
  margin: 0 0 .55rem;
  font-family: var(--font-display);
  font-size: clamp(1.2rem, 4.6vw, 1.72rem);
  font-weight: 700;
  line-height: 1.36;
  color: var(--text);
}

.page-about .chapter-desc {
  margin: 0;
  max-width: 60ch;
  font-size: .92rem;
  line-height: 1.8;
  color: var(--muted);
}

.page-about .chapter-meta {
  display: none;
  writing-mode: vertical-rl;
  font-family: var(--font-mono);
  font-size: .68rem;
  letter-spacing: .2em;
  color: var(--muted-dim);
}

/* ---------- 刻度分隔线 ---------- */

.page-about .ruler {
  height: 10px;
  margin: 1.4rem 0;
  border: 0;
  background-image: repeating-linear-gradient(to right, var(--grid) 0 1px, transparent 1px 11px);
  background-repeat: repeat-x;
  background-size: auto 10px;
  background-position: 0 100%;
  opacity: .85;
}

/* ---------- 01 时间轴 ---------- */

.page-about .era-track {
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: minmax(216px, 78%);
  gap: .9rem;
  margin: 0;
  padding: 1rem .2rem 1.3rem;
  list-style: none;
  overflow-x: auto;
  scroll-snap-type: x proximity;
  -webkit-overflow-scrolling: touch;
}

.page-about .era-node {
  position: relative;
  scroll-snap-align: start;
  padding: 1.25rem 1rem 1.25rem;
  background: var(--about-panel);
  border: 1px solid var(--about-line);
  border-radius: var(--radius-b);
  transition: transform .28s var(--ease), border-color .28s var(--ease);
}

.page-about .era-node::before {
  content: "";
  position: absolute;
  top: -5px;
  left: 1rem;
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--cyan);
  box-shadow: 0 0 0 3px var(--about-glow);
}

.page-about .era-node:hover {
  transform: translateY(-3px);
  border-color: var(--cyan-deep);
}

.page-about .era-year {
  display: block;
  font-family: var(--font-mono);
  font-size: 1.35rem;
  font-weight: 700;
  letter-spacing: -.02em;
  color: var(--amber);
}

.page-about .era-name {
  margin: .4rem 0 .5rem;
  font-size: .96rem;
  font-weight: 700;
  color: var(--text);
}

.page-about .era-text {
  margin: 0;
  font-size: .84rem;
  line-height: 1.74;
  color: var(--muted);
}

/* ---------- 02 数据来源 ---------- */

.page-about .source-grid {
  display: grid;
  gap: 1.4rem;
}

.page-about .source-text p {
  margin: 0 0 1rem;
  font-size: .93rem;
  line-height: 1.85;
  color: var(--muted);
}

.page-about .source-list {
  margin: 1.2rem 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: .6rem;
}

.page-about .source-list li {
  display: flex;
  align-items: center;
  gap: .65rem;
  padding: .68rem .9rem;
  font-size: .86rem;
  color: var(--text);
  background: var(--about-panel);
  border: 1px solid var(--about-line-soft);
  border-radius: var(--radius-b);
}

.page-about .source-mark {
  flex: 0 0 auto;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--cyan);
  box-shadow: 0 0 0 3px var(--about-glow);
}

.page-about .flow-figure {
  margin: 0;
  border: 1px solid var(--about-line);
  border-radius: var(--radius-a);
  overflow: hidden;
  background: var(--about-panel);
}

.page-about .flow-figure img {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 3 / 2;
  object-fit: cover;
}

.page-about .flow-figure figcaption {
  padding: .7rem .95rem;
  font-family: var(--font-mono);
  font-size: .7rem;
  letter-spacing: .06em;
  color: var(--muted);
  border-top: 1px solid var(--about-line-soft);
}

.page-about .source-notes {
  display: grid;
  gap: .9rem;
  margin-top: 1.6rem;
}

.page-about .source-note {
  padding: 1.1rem 1.1rem 1.2rem;
  background: var(--about-panel);
  border: 1px solid var(--about-line-soft);
  border-radius: var(--radius-b);
  border-top: 2px solid var(--cyan-deep);
}

.page-about .source-note h3 {
  margin: 0 0 .5rem;
  font-size: .95rem;
  font-weight: 700;
  color: var(--text);
}

.page-about .source-note p {
  margin: 0;
  font-size: .85rem;
  line-height: 1.76;
  color: var(--muted);
}

/* ---------- 03 团队 ---------- */

.page-about .role-list {
  display: grid;
  gap: .7rem;
}

.page-about .role-item {
  background: var(--about-panel);
  border: 1px solid var(--about-line);
  border-radius: var(--radius-b);
  overflow: hidden;
}

.page-about .role-item summary {
  display: flex;
  align-items: center;
  gap: .7rem;
  padding: 1rem 1.1rem;
  font-size: .95rem;
  font-weight: 700;
  color: var(--text);
  cursor: pointer;
  list-style: none;
}

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

.page-about .role-item summary::before {
  content: "";
  flex: 0 0 auto;
  width: 9px;
  height: 9px;
  border-radius: 2px;
  background: var(--cyan);
  transition: background-color .24s var(--ease);
}

.page-about .role-item[open] summary::before {
  background: var(--amber);
}

.page-about .role-item p {
  margin: 0;
  padding: 0 1.1rem 1.15rem 1.85rem;
  font-size: .86rem;
  line-height: 1.8;
  color: var(--muted);
}

.page-about .team-note {
  margin: 1.5rem 0 0;
  padding: 1rem 1.1rem;
  font-size: .86rem;
  line-height: 1.8;
  color: var(--muted);
  background: linear-gradient(135deg, rgba(15, 185, 166, .1), rgba(5, 11, 24, 0) 70%);
  border-left: 2px solid var(--cyan);
  border-radius: 0 var(--radius-b) var(--radius-b) 0;
}

/* ---------- 04 覆盖与归档 ---------- */

.page-about .coverage-grid {
  display: grid;
  gap: 1.4rem;
}

.page-about .coverage-figure {
  margin: 0;
  border: 1px solid var(--about-line);
  border-radius: var(--radius-a);
  overflow: hidden;
  background: var(--about-panel);
}

.page-about .coverage-figure img {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 4 / 3;
  object-fit: cover;
}

.page-about .coverage-figure figcaption {
  padding: .7rem .95rem;
  font-family: var(--font-mono);
  font-size: .7rem;
  letter-spacing: .06em;
  color: var(--muted);
  border-top: 1px solid var(--about-line-soft);
}

.page-about .archive-steps h3 {
  margin: 0 0 1rem;
  font-size: 1.02rem;
  font-weight: 700;
  color: var(--text);
}

.page-about .archive-steps ol {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: .75rem;
}

.page-about .archive-steps li {
  padding: .85rem .95rem;
  background: var(--about-panel);
  border: 1px solid var(--about-line-soft);
  border-radius: var(--radius-b);
}

.page-about .step-key {
  display: inline-block;
  margin-bottom: .35rem;
  font-family: var(--font-mono);
  font-size: .72rem;
  letter-spacing: .14em;
  color: var(--violet-soft);
}

.page-about .archive-steps p {
  margin: 0;
  font-size: .85rem;
  line-height: 1.74;
  color: var(--muted);
}

.page-about .league-groups {
  display: grid;
  gap: .6rem;
  margin-top: 1.6rem;
}

.page-about .league-group {
  background: var(--about-panel);
  border: 1px solid var(--about-line-soft);
  border-radius: var(--radius-b);
  overflow: hidden;
}

.page-about .league-group summary {
  padding: .8rem 1rem;
  font-size: .9rem;
  font-weight: 700;
  color: var(--text);
  cursor: pointer;
  list-style: none;
  position: relative;
  padding-right: 2.4rem;
}

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

.page-about .league-group summary::after {
  content: "+";
  position: absolute;
  right: 1rem;
  top: 50%;
  transform: translateY(-50%);
  font-family: var(--font-mono);
  font-size: 1rem;
  color: var(--cyan);
}

.page-about .league-group[open] summary::after {
  content: "–";
}

.page-about .league-tags {
  display: flex;
  flex-wrap: wrap;
  gap: .45rem;
  margin: 0;
  padding: 0 1rem 1rem;
  list-style: none;
}

.page-about .league-tags li {
  padding: .3rem .72rem;
  font-size: .78rem;
  color: var(--muted);
  background: rgba(20, 36, 63, .9);
  border: 1px solid var(--about-line);
  border-radius: 999px;
}

/* ---------- 05 合作 ---------- */

.page-about .partner-grid {
  display: grid;
  gap: .9rem;
}

.page-about .partner-card {
  padding: 1.15rem 1.1rem 1.25rem;
  background: var(--about-panel);
  border: 1px solid var(--about-line);
  border-radius: var(--radius-a);
}

.page-about .partner-num {
  display: block;
  font-family: var(--font-mono);
  font-size: 1.7rem;
  font-weight: 700;
  letter-spacing: -.03em;
  color: var(--amber);
  text-shadow: 0 0 22px var(--about-amber-glow);
}

.page-about .partner-card h3 {
  margin: .45rem 0 .5rem;
  font-size: .95rem;
  font-weight: 700;
  color: var(--text);
}

.page-about .partner-card p {
  margin: 0;
  font-size: .84rem;
  line-height: 1.76;
  color: var(--muted);
}

.page-about .partner-note {
  margin: 1.5rem 0 0;
  font-size: .88rem;
  line-height: 1.85;
  color: var(--muted);
  max-width: 62ch;
}

/* ---------- 06 下一步 ---------- */

.page-about .next-list {
  display: grid;
  gap: .8rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

.page-about .next-list li {
  padding: 1rem 1.1rem;
  background: var(--about-panel);
  border: 1px solid var(--about-line-soft);
  border-left: 2px solid var(--violet);
  border-radius: 0 var(--radius-b) var(--radius-b) 0;
}

.page-about .next-list h3 {
  margin: 0 0 .4rem;
  font-size: .93rem;
  font-weight: 700;
  color: var(--text);
}

.page-about .next-list p {
  margin: 0;
  font-size: .84rem;
  line-height: 1.76;
  color: var(--muted);
}

.page-about .cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: .7rem;
  margin-top: 1.8rem;
}

.page-about .cta-row .btn {
  flex: 1 1 auto;
  text-align: center;
  min-width: 140px;
}

/* ---------- 桌面端 ---------- */

@media (min-width: 640px) {
  .page-about .hero-stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

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

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

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

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

@media (min-width: 880px) {
  .page-about .chapter {
    padding: 3.2rem 0 2rem;
  }

  .page-about .chapter-head {
    grid-template-columns: auto minmax(0, 1fr) auto;
    gap: 1rem 1.6rem;
    margin-bottom: 2rem;
  }

  .page-about .chapter-meta {
    display: block;
    margin-top: .2rem;
  }

  .page-about .era-track {
    grid-auto-flow: row;
    grid-template-columns: repeat(5, minmax(0, 1fr));
    grid-auto-columns: auto;
    gap: .85rem;
    overflow: visible;
    padding-bottom: .8rem;
  }

  .page-about .source-grid {
    grid-template-columns: minmax(0, 1.05fr) minmax(0, .95fr);
    gap: 2rem;
    align-items: start;
  }

  .page-about .coverage-grid {
    grid-template-columns: minmax(0, .92fr) minmax(0, 1.08fr);
    gap: 2rem;
    align-items: start;
  }

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

  .page-about .cta-row .btn {
    flex: 0 0 auto;
  }

  .page-about .ruler {
    margin: 2rem 0;
  }
}

@media (min-width: 1100px) {
  .page-about .about-hero {
    padding-top: 2.4rem;
    padding-bottom: 3rem;
  }

  .page-about .cover-frame {
    margin-top: 2.8rem;
  }

  .page-about .chapter-nav {
    margin-top: 2rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .era-node,
  .page-about .chapter-nav a,
  .page-about .role-item summary::before {
    transition: none;
  }

  .page-about .era-node:hover {
    transform: none;
  }
}