.page-about {
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-body);
  overflow-x: hidden;
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  overflow: hidden;
  background: var(--deep);
  color: var(--paper);
  padding: 32px 0 40px;
  border-bottom: 1px solid var(--line-light);
}

.page-about .about-hero::before {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  background:
    repeating-linear-gradient(90deg, transparent 0 47px, rgba(247, 240, 228, .06) 47px 48px),
    repeating-linear-gradient(0deg, transparent 0 47px, rgba(247, 240, 228, .04) 47px 48px),
    radial-gradient(90% 70% at 88% 0%, rgba(35, 230, 211, .18), transparent 62%),
    radial-gradient(70% 60% at 0% 100%, rgba(200, 16, 46, .24), transparent 62%);
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  width: 6px;
  height: 96px;
  background: var(--arena-red);
}

.page-about .about-hero__inner {
  position: relative;
  z-index: 1;
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 0 20px;
  display: grid;
  gap: 30px;
}

.page-about .about-hero__label {
  color: var(--neon);
  letter-spacing: .2em;
}

.page-about .about-hero__title {
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(30px, 7vw, 56px);
  line-height: 1.08;
  letter-spacing: -.02em;
  margin: 14px 0 0;
  color: var(--white);
  text-wrap: balance;
}

.page-about .about-hero__lead {
  margin: 16px 0 0;
  max-width: 48ch;
  font-size: 16px;
  line-height: 1.78;
  color: var(--paper-72);
}

.page-about .about-hero__flags {
  list-style: none;
  margin: 22px 0 0;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 8px 16px;
}

.page-about .about-hero__flags li {
  position: relative;
  padding-left: 14px;
  font-size: 13px;
  line-height: 1.6;
  color: var(--paper-72);
}

.page-about .about-hero__flags li::before {
  content: "";
  position: absolute;
  left: 0;
  top: .52em;
  width: 6px;
  height: 6px;
  background: var(--amber);
  transform: rotate(45deg);
}

.page-about .about-stats {
  margin: 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  background: var(--line-light);
  border: 1px solid var(--line-light);
}

.page-about .about-stats__item {
  background: rgba(14, 42, 71, .9);
  padding: 14px 14px 16px;
}

.page-about .about-stats__term {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: .1em;
  color: var(--paper-55);
}

.page-about .about-stats__value {
  margin: 6px 0 0;
  display: flex;
  align-items: baseline;
  gap: 3px;
}

.page-about .about-stats__num {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: clamp(24px, 6vw, 32px);
  line-height: 1;
  color: var(--neon);
  font-variant-numeric: tabular-nums;
}

.page-about .about-stats__unit {
  font-size: 12px;
  color: var(--paper-55);
}

/* ---------- 主体布局 ---------- */
.page-about .about-body {
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 44px 20px 72px;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 34px;
}

.page-about .about-index__label {
  color: var(--slate);
}

.page-about .about-index__list {
  list-style: none;
  margin: 10px 0 0;
  padding: 0 0 8px;
  display: flex;
  gap: 8px;
  overflow-x: auto;
  scrollbar-width: none;
}

.page-about .about-index__list::-webkit-scrollbar {
  display: none;
}

.page-about .about-index__link {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  white-space: nowrap;
  padding: 7px 12px;
  border: 1px solid var(--line-strong);
  background: var(--white);
  color: var(--ink);
  font-size: 13px;
  text-decoration: none;
  transition: border-color var(--dur) var(--ease), color var(--dur) var(--ease), background var(--dur) var(--ease);
}

.page-about .about-index__link:hover,
.page-about .about-index__link:focus-visible {
  border-color: var(--arena-red);
  color: var(--arena-red);
  background: var(--paper);
}

.page-about .about-index__num {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--clay);
}

.page-about .about-chapters {
  display: grid;
  gap: 48px;
  min-width: 0;
}

/* ---------- 章节通用 ---------- */
.page-about .chapter {
  scroll-margin-top: 24px;
  padding-bottom: 40px;
  border-bottom: 1px solid var(--line);
}

.page-about .chapter:last-child {
  border-bottom: 0;
  padding-bottom: 0;
}

.page-about .chapter__head {
  display: grid;
  gap: 10px;
  margin-bottom: 22px;
}

.page-about .chapter__num {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .2em;
  color: var(--clay);
}

.page-about .chapter__title {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(23px, 5.2vw, 36px);
  line-height: 1.2;
  letter-spacing: -.01em;
  margin: 0;
  max-width: 22ch;
}

.page-about .chapter p {
  font-size: 16px;
  line-height: 1.8;
  color: var(--ink);
}

.page-about .chapter__lead {
  margin: 0 0 24px;
  max-width: 60ch;
  color: var(--slate) !important;
  font-size: 16px;
  line-height: 1.8;
}

/* ---------- 01 起点 ---------- */
.page-about .origin-grid {
  display: grid;
  gap: 24px;
}

.page-about .origin-copy p {
  margin: 0 0 14px;
}

.page-about .origin-steps {
  list-style: none;
  margin: 20px 0 0;
  padding: 0;
  display: grid;
  gap: 10px;
}

.page-about .origin-steps__item {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr);
  gap: 12px;
  align-items: start;
  padding-top: 10px;
  border-top: 1px solid var(--line);
}

.page-about .origin-steps__num {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--clay);
  padding-top: 4px;
}

.page-about .origin-steps__item p {
  margin: 0;
  font-size: 15px;
  color: var(--slate);
}

.page-about .origin-aside {
  background: var(--midnight);
  color: var(--paper);
  padding: 22px 20px;
  border-left: 4px solid var(--arena-red);
  transform: rotate(-.6deg);
}

.page-about .origin-aside__label {
  color: var(--neon);
  margin: 0;
}

.page-about .origin-aside__list {
  list-style: none;
  margin: 14px 0 0;
  padding: 0;
  display: grid;
  gap: 9px;
}

.page-about .origin-aside__list li {
  font-size: 14px;
  line-height: 1.5;
  color: var(--paper-72);
  padding-left: 12px;
  position: relative;
}

.page-about .origin-aside__list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: .55em;
  width: 5px;
  height: 5px;
  background: var(--neon);
}

/* ---------- 图片 ---------- */
.page-about .about-figure {
  margin: 0 0 24px;
  border: 1px solid var(--line-strong);
  background: var(--midnight);
}

.page-about .about-figure img {
  display: block;
  width: 100%;
  height: auto;
  max-width: 100%;
  object-fit: cover;
  aspect-ratio: 16 / 10;
}

.page-about .about-figure--tall img {
  aspect-ratio: 14 / 9;
}

.page-about .about-figure__cap {
  font-family: var(--font-mono);
  font-size: 12px;
  line-height: 1.6;
  color: var(--paper-72);
  padding: 10px 12px;
  border-top: 1px solid var(--line-light);
}

/* ---------- 02 服务网络 ---------- */
.page-about .network-grid {
  display: grid;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  margin-bottom: 22px;
}

.page-about .network-card {
  background: var(--white);
  padding: 18px 16px;
  border-left: 3px solid var(--clay);
}

.page-about .network-card__num {
  display: block;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: clamp(28px, 7vw, 38px);
  line-height: 1;
  color: var(--deep);
  font-variant-numeric: tabular-nums;
}

.page-about .network-card__title {
  margin: 6px 0 8px;
  font-size: 16px;
  font-weight: 700;
  color: var(--arena-red);
}

.page-about .network-card p {
  margin: 0;
  font-size: 14px;
  line-height: 1.7;
  color: var(--slate);
}

.page-about .network-map {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 8px;
  padding: 14px;
  border: 1px solid var(--line-strong);
  background: var(--white);
}

.page-about .network-map__node {
  display: flex;
  align-items: center;
  justify-content: center;
  aspect-ratio: 1 / 1;
  border: 1px solid var(--line-strong);
  background: linear-gradient(140deg, rgba(35, 230, 211, .12), transparent 68%);
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--slate);
}

.page-about .network-map__node--key {
  background: var(--arena-red);
  border-color: var(--arena-red);
  color: var(--white);
}

.page-about .network-map__note {
  margin: 10px 0 22px;
  font-size: 13px;
  line-height: 1.7;
  color: var(--slate);
}

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

.page-about .network-flow__step {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 11px 14px;
  background: var(--deep);
  border-left: 3px solid var(--neon);
}

.page-about .network-flow__num {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--neon);
}

.page-about .network-flow__text {
  font-size: 14px;
  font-weight: 600;
  color: var(--paper);
  letter-spacing: .02em;
}

/* ---------- 03 团队 ---------- */
.page-about .team-grid {
  display: grid;
  gap: 22px;
}

.page-about .team-copy p {
  margin: 0 0 14px;
}

.page-about .team-facts {
  margin: 20px 0 0;
  display: grid;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .team-facts__row {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 6px 14px;
  background: var(--white);
  padding: 11px 13px;
}

.page-about .team-facts__term {
  font-size: 13px;
  color: var(--slate);
}

.page-about .team-facts__value {
  margin: 0;
  font-size: 14px;
  font-weight: 700;
  color: var(--ink);
}

.page-about .principle-switch {
  position: relative;
  margin-top: 26px;
  padding: 20px 18px;
  border: 1px solid var(--line-strong);
  background: var(--white);
  display: grid;
  gap: 14px;
}

.page-about .principle-switch:focus-within {
  outline: 2px solid var(--amber);
  outline-offset: 3px;
}

.page-about .principle-switch__label {
  color: var(--slate);
  margin: 0;
}

.page-about .principle-switch__input {
  position: absolute;
  width: 1px;
  height: 1px;
  opacity: 0;
  pointer-events: none;
}

.page-about .principle-switch__tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.page-about .principle-switch__tab {
  cursor: pointer;
  padding: 8px 14px;
  border: 1px solid var(--line-strong);
  font-size: 14px;
  font-weight: 600;
  color: var(--ink);
  background: var(--paper);
  transition: background var(--dur) var(--ease), color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}

.page-about .principle-switch__tab:hover {
  border-color: var(--arena-red);
  color: var(--arena-red);
}

.page-about .principle-switch__panel {
  display: none;
}

.page-about .principle-switch__panel p {
  margin: 0;
  font-size: 15px;
  line-height: 1.8;
  color: var(--ink);
}

.page-about #train-tablet:checked ~ .principle-switch__tabs label[for="train-tablet"],
.page-about #train-etiquette:checked ~ .principle-switch__tabs label[for="train-etiquette"],
.page-about #train-privacy:checked ~ .principle-switch__tabs label[for="train-privacy"] {
  background: var(--arena-red);
  border-color: var(--arena-red);
  color: var(--white);
}

.page-about #train-tablet:checked ~ .principle-switch__panels #panel-tablet,
.page-about #train-etiquette:checked ~ .principle-switch__panels #panel-etiquette,
.page-about #train-privacy:checked ~ .principle-switch__panels #panel-privacy {
  display: block;
}

/* ---------- 04 质量保障 ---------- */
.page-about .record-pair {
  display: grid;
  gap: 1px;
  background: var(--line-strong);
  border: 1px solid var(--line-strong);
  margin-bottom: 24px;
}

.page-about .record-pair__item {
  background: var(--white);
  padding: 18px 16px;
}

.page-about .record-pair__tag {
  margin: 0;
  color: var(--clay);
}

.page-about .record-pair__title {
  margin: 8px 0 8px;
  font-size: 17px;
  font-weight: 700;
}

.page-about .record-pair__text {
  margin: 0;
  font-size: 14px;
  line-height: 1.75;
  color: var(--slate);
}

.page-about .record-pair__join {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 10px;
  background: var(--ink);
  color: var(--neon);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .18em;
}

.page-about .quality-flow {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
}

.page-about .quality-flow__step {
  border-top: 2px solid var(--clay);
  padding-top: 10px;
}

.page-about .quality-flow__num {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--clay);
}

.page-about .quality-flow__name {
  display: block;
  margin: 5px 0 3px;
  font-size: 16px;
  font-weight: 700;
}

.page-about .quality-flow__desc {
  display: block;
  font-size: 13px;
  line-height: 1.65;
  color: var(--slate);
}

/* ---------- 05 时间线 ---------- */
.page-about .timeline {
  list-style: none;
  margin: 0;
  padding: 0 0 0 26px;
  position: relative;
}

.page-about .timeline::before {
  content: "";
  position: absolute;
  left: 7px;
  top: 12px;
  bottom: 12px;
  width: 2px;
  background: var(--line-strong);
}

.page-about .timeline__item {
  position: relative;
  padding-bottom: 12px;
}

.page-about .timeline__item::before {
  content: "";
  position: absolute;
  left: -24px;
  top: 12px;
  width: 12px;
  height: 12px;
  background: var(--clay);
  transition: background var(--dur) var(--ease);
}

.page-about .timeline__item:hover::before {
  background: var(--arena-red);
}

.page-about .timeline__summary {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 6px 14px;
  list-style: none;
  cursor: pointer;
  padding: 6px 0;
}

.page-about .timeline__summary::-webkit-details-marker {
  display: none;
}

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

.page-about .timeline__year {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: clamp(20px, 5vw, 28px);
  line-height: 1;
  color: var(--deep);
  font-variant-numeric: tabular-nums;
  transition: color var(--dur) var(--ease);
}

.page-about .timeline__node[open] .timeline__year {
  color: var(--arena-red);
}

.page-about .timeline__title {
  font-size: 15px;
  font-weight: 700;
  color: var(--ink);
}

.page-about .timeline__text {
  margin: 2px 0 12px;
  font-size: 14px;
  line-height: 1.8;
  color: var(--slate);
  border-left: 2px solid var(--line);
  padding-left: 12px;
}

/* ---------- 06 持续服务 ---------- */
.page-about .why-panel {
  background: var(--deep);
  color: var(--paper);
  padding: 26px 20px;
  border-top: 4px solid var(--arena-red);
}

.page-about .why-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px 14px;
}

.page-about .why-card__num {
  display: block;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: clamp(24px, 6vw, 34px);
  line-height: 1;
  color: var(--neon);
  font-variant-numeric: tabular-nums;
}

.page-about .why-card__label {
  margin: 8px 0 0;
  font-size: 13px !important;
  line-height: 1.65 !important;
  color: var(--paper-72) !important;
}

.page-about .why-actions {
  margin-top: 26px;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 14px 20px;
}

.page-about .why-link {
  color: var(--paper);
  font-size: 14px;
  font-weight: 600;
  text-decoration: none;
  border-bottom: 1px solid var(--neon);
  padding-bottom: 2px;
  transition: color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}

.page-about .why-link:hover,
.page-about .why-link:focus-visible {
  color: var(--neon);
  border-color: var(--amber);
}

.page-about .why-note {
  margin: 18px 0 0;
  font-size: 13px !important;
  line-height: 1.75 !important;
  color: var(--paper-55) !important;
}

.page-about .why-note__link {
  color: var(--neon);
  text-decoration: none;
  border-bottom: 1px solid var(--line-light);
  margin-left: 3px;
}

.page-about .why-note__link:hover,
.page-about .why-note__link:focus-visible {
  color: var(--amber);
  border-color: var(--amber);
}

/* ---------- 断点 ---------- */
@media (min-width: 720px) {
  .page-about .about-hero {
    padding: 52px 0 60px;
  }

  .page-about .about-hero__inner {
    grid-template-columns: minmax(0, 1.4fr) minmax(0, 1fr);
    align-items: end;
    gap: 44px;
    padding: 0 32px;
  }

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

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

  .page-about .network-map {
    grid-template-columns: repeat(6, minmax(0, 1fr));
    padding: 18px;
  }

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

  .page-about .network-flow__step {
    flex-direction: column;
    align-items: flex-start;
    gap: 6px;
  }

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

  .page-about .record-pair {
    grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr);
  }

  .page-about .record-pair__join {
    writing-mode: vertical-rl;
    padding: 18px 8px;
  }

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

  .page-about .why-panel {
    padding: 32px 28px;
  }
}

@media (min-width: 960px) {
  .page-about .about-body {
    grid-template-columns: 180px minmax(0, 1fr);
    gap: 56px;
    padding: 66px 32px 96px;
  }

  .page-about .about-index {
    position: sticky;
    top: 24px;
    align-self: start;
  }

  .page-about .about-index__list {
    flex-direction: column;
    overflow: visible;
    gap: 0;
    padding: 0;
    border-left: 1px solid var(--line-strong);
  }

  .page-about .about-index__item {
    margin-left: -1px;
  }

  .page-about .about-index__link {
    display: flex;
    width: 100%;
    border: 0;
    border-left: 2px solid transparent;
    background: none;
    padding: 9px 0 9px 13px;
    white-space: normal;
    font-size: 13px;
  }

  .page-about .about-index__link:hover,
  .page-about .about-index__link:focus-visible {
    background: linear-gradient(90deg, rgba(200, 16, 46, .08), transparent 80%);
    border-left-color: var(--arena-red);
    color: var(--arena-red);
  }

  .page-about .about-chapters {
    gap: 60px;
  }

  .page-about .chapter {
    scroll-margin-top: 40px;
    padding-bottom: 52px;
  }

  .page-about .origin-grid {
    grid-template-columns: minmax(0, 1.55fr) minmax(0, 1fr);
    gap: 32px;
    align-items: start;
  }

  .page-about .team-grid {
    grid-template-columns: minmax(0, 1.1fr) minmax(0, 1fr);
    gap: 32px;
    align-items: start;
  }

  .page-about .team-grid .about-figure {
    margin-bottom: 0;
  }

  .page-about .principle-switch {
    margin-top: 32px;
    padding: 24px 22px;
  }

  .page-about .principle-switch__panel p {
    max-width: 72ch;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-index__link,
  .page-about .principle-switch__tab,
  .page-about .timeline__year,
  .page-about .why-link {
    transition: none;
  }

  .page-about .origin-aside {
    transform: none;
  }
}