.page-about {
  display: block;
  overflow-x: clip;
}

.page-about .breadcrumbs {
  padding-block: 18px 0;
}

.page-about .breadcrumbs__list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 0;
  padding: 0;
  list-style: none;
  font-size: 13px;
  color: var(--muted);
}

.page-about .breadcrumbs__list li + li::before {
  content: "›";
  margin-right: 8px;
  color: var(--line);
}

.page-about .breadcrumbs__list a {
  color: var(--muted);
  text-decoration: none;
}

.page-about .breadcrumbs__list a:hover {
  color: var(--cyan);
}

/* ---------- 首屏 ---------- */

.page-about .about-hero {
  position: relative;
  padding-block: clamp(26px, 5vw, 60px) clamp(34px, 6vw, 74px);
  overflow: hidden;
}

.page-about .about-hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(to right, rgba(30, 58, 110, 0.32) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(30, 58, 110, 0.32) 1px, transparent 1px);
  background-size: 64px 64px;
  opacity: 0.55;
  pointer-events: none;
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  top: -40%;
  right: -20%;
  width: min(520px, 65vw);
  height: 180%;
  background: linear-gradient(110deg, transparent 38%, rgba(34, 224, 214, 0.14) 50%, transparent 62%);
  transform: rotate(10deg);
  pointer-events: none;
}

.page-about .about-hero__grid {
  position: relative;
  display: grid;
  gap: 30px;
}

.page-about .about-hero h1 {
  margin: 12px 0 0;
  font-size: clamp(34px, 7vw, 88px);
  line-height: 1.04;
  letter-spacing: -0.02em;
  font-weight: 800;
  color: var(--text);
}

.page-about .about-hero__lead {
  margin: 22px 0 0;
  max-width: 34em;
  font-size: 16px;
  line-height: 1.8;
  color: var(--text-dim);
}

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

.page-about .hero-facts {
  margin: 0;
  display: grid;
  gap: 12px;
  padding: 18px;
  border: var(--edge);
  background: var(--panel);
  box-shadow: var(--shadow-hard);
}

.page-about .hero-facts__row {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--line);
}

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

.page-about .hero-facts dt {
  font-size: 13px;
  color: var(--muted);
}

.page-about .hero-facts dd {
  margin: 0;
  font-size: 14px;
  color: var(--text);
}

.page-about .hero-facts dd .mono {
  font-size: 20px;
  color: var(--cyan);
}

/* ---------- 通用章节 ---------- */

.page-about .section {
  padding-block: clamp(40px, 6vw, 78px);
}

.page-about .section h2 {
  margin: 0;
  font-size: clamp(23px, 3.2vw, 38px);
  line-height: 1.16;
  letter-spacing: -0.015em;
  font-weight: 800;
  color: var(--text);
}

.page-about .section__sub {
  margin: 14px 0 0;
  max-width: 34em;
  font-size: 15px;
  line-height: 1.75;
  color: var(--muted);
}

.page-about .eyebrow {
  color: var(--cyan);
}

.page-about .shot {
  margin: 0;
  border: var(--edge);
  background: var(--panel-2);
  box-shadow: var(--shadow-hard);
}

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

.page-about .shot .figure__caption {
  display: block;
  padding: 10px 14px;
  border-top: 1px solid var(--line);
  font-size: 13px;
  line-height: 1.6;
  color: var(--muted);
}

/* ---------- 起点 ---------- */

.page-about .origin-grid {
  display: grid;
  gap: 30px;
}

.page-about .origin-copy p {
  margin: 18px 0 0;
  max-width: 34em;
  font-size: 16px;
  line-height: 1.8;
  color: var(--text-dim);
}

.page-about .fact-list {
  margin: 26px 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 12px;
}

.page-about .fact-list li {
  display: flex;
  gap: 12px;
  align-items: baseline;
  padding-left: 12px;
  border-left: 2px solid var(--line);
  font-size: 15px;
  line-height: 1.7;
  color: var(--text-dim);
}

.page-about .fact-list .mono {
  flex: none;
  font-size: 13px;
  color: var(--orange);
  letter-spacing: 0.08em;
}

/* ---------- 时间轴 ---------- */

.page-about .tl-banner {
  margin-bottom: clamp(28px, 4vw, 46px);
}

.page-about .tl {
  display: grid;
  gap: 22px;
}

.page-about .tl__rail {
  display: flex;
  gap: 8px;
  margin: 0;
  padding: 2px 2px 10px;
  list-style: none;
  overflow-x: auto;
}

.page-about .tl__rail li {
  flex: none;
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 6px 10px;
  border: 1px solid var(--line);
  background: var(--panel);
}

.page-about .tl__rail li::before {
  content: "";
  flex: none;
  width: 9px;
  height: 9px;
  border: 2px solid var(--cyan);
  border-radius: 50%;
  background: transparent;
}

.page-about .tl__rail a {
  display: flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--muted);
  text-decoration: none;
  white-space: nowrap;
}

.page-about .tl__rail a:hover {
  color: var(--cyan-hi);
}

.page-about .tl__rail li[data-active="true"] {
  border-color: var(--cyan);
}

.page-about .tl__rail li[data-active="true"]::before {
  background: var(--red);
  border-color: var(--red);
  box-shadow: 0 0 0 4px rgba(225, 42, 74, 0.16);
}

.page-about .tl__rail li[data-active="true"] a {
  color: var(--cyan);
}

.page-about .stage {
  position: relative;
  padding: 20px 18px 22px;
  border: var(--edge);
  background: var(--panel);
  box-shadow: var(--shadow-hard);
}

.page-about .stage:nth-child(even) {
  background: var(--panel-2);
}

.page-about .stage + .stage {
  margin-top: 22px;
}

.page-about .stage--key {
  border-color: rgba(34, 224, 214, 0.55);
}

.page-about .stage__top {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 14px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--line);
}

.page-about .stage__num {
  font-size: clamp(26px, 4vw, 40px);
  line-height: 1;
  color: var(--cyan);
  letter-spacing: 0.02em;
}

.page-about .stage__when {
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--muted);
}

.page-about .stage h3 {
  margin: 16px 0 0;
  font-size: 19px;
  line-height: 1.35;
  letter-spacing: -0.01em;
  font-weight: 700;
  color: var(--text);
}

.page-about .stage__lede {
  margin: 10px 0 0;
  font-size: 15px;
  line-height: 1.75;
  color: var(--text-dim);
}

.page-about .stage__facts {
  margin: 16px 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 10px;
}

.page-about .stage__facts li {
  position: relative;
  padding: 10px 0 0 22px;
  border-top: 1px solid var(--line);
  font-size: 14px;
  line-height: 1.7;
  color: var(--muted);
}

.page-about .stage__facts li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 18px;
  width: 11px;
  height: 2px;
  background: var(--orange);
}

/* ---------- 呼吸区 ---------- */

.page-about .about-breath {
  position: relative;
  margin-block: clamp(36px, 6vw, 88px);
  padding-block: clamp(54px, 9vw, 118px);
  border-top: 2px solid var(--graphite);
  border-bottom: 2px solid var(--graphite);
  background:
    radial-gradient(120% 90% at 12% 50%, rgba(34, 224, 214, 0.10), transparent 62%),
    linear-gradient(180deg, #04070F 0%, #060B18 55%, #04070F 100%);
  overflow: hidden;
}

.page-about .about-breath__quote {
  margin: 0;
  max-width: 22em;
  font-size: clamp(22px, 3.6vw, 42px);
  line-height: 1.34;
  letter-spacing: -0.015em;
  font-weight: 800;
  color: var(--text);
}

.page-about .about-breath__quote::before {
  content: "“";
  display: block;
  margin-bottom: 6px;
  font-family: var(--font-mono);
  font-size: clamp(56px, 10vw, 132px);
  line-height: 0.65;
  color: rgba(34, 224, 214, 0.38);
}

.page-about .about-breath__note {
  margin: 24px 0 0;
  font-size: 12px;
  letter-spacing: 0.1em;
  color: var(--muted);
}

/* ---------- 2025 年 3 月 ---------- */

.page-about .v4-grid {
  display: grid;
  gap: 30px;
}

.page-about .v4-copy > p {
  margin: 18px 0 0;
  max-width: 34em;
  font-size: 16px;
  line-height: 1.8;
  color: var(--text-dim);
}

.page-about .v4-changes {
  margin: 28px 0 30px;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 18px;
}

.page-about .v4-changes li {
  display: grid;
  grid-template-columns: 44px minmax(0, 1fr);
  gap: 14px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
}

.page-about .v4-changes__num {
  font-size: 15px;
  color: var(--orange);
  letter-spacing: 0.08em;
  padding-top: 2px;
}

.page-about .v4-changes h3 {
  margin: 0;
  font-size: 17px;
  line-height: 1.4;
  font-weight: 700;
  color: var(--text);
}

.page-about .v4-changes p {
  margin: 8px 0 0;
  font-size: 14.5px;
  line-height: 1.75;
  color: var(--muted);
}

/* ---------- 维护 ---------- */

.page-about .maint-grid {
  display: grid;
  gap: 26px;
  margin-top: 30px;
}

.page-about .nav-index {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 0;
  border-top: 2px solid var(--graphite);
}

.page-about .nav-index li {
  display: grid;
  grid-template-columns: 42px minmax(0, 1fr);
  gap: 14px;
  padding-block: 16px;
  border-bottom: 1px solid var(--line);
}

.page-about .nav-index .mono {
  font-size: 14px;
  color: var(--cyan);
  letter-spacing: 0.08em;
}

.page-about .nav-index strong {
  display: block;
  font-size: 16px;
  font-weight: 700;
  color: var(--text);
}

.page-about .nav-index p {
  margin: 6px 0 0;
  font-size: 14px;
  line-height: 1.7;
  color: var(--muted);
}

.page-about .maint-team {
  padding: 22px 18px;
}

.page-about .maint-team__label {
  margin: 0 0 6px;
  font-size: 12px;
  letter-spacing: 0.12em;
  color: var(--cyan);
}

.page-about .maint-team__row {
  padding-block: 14px;
  border-bottom: 1px solid var(--line);
}

.page-about .maint-team__row h3 {
  margin: 0;
  font-size: 16px;
  font-weight: 700;
  color: var(--text);
}

.page-about .maint-team__row p {
  margin: 8px 0 0;
  font-size: 14px;
  line-height: 1.7;
  color: var(--muted);
}

.page-about .maint-team__foot {
  margin: 16px 0 0;
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--text-dim);
}

/* ---------- 站点信息 ---------- */

.page-about .service-grid {
  display: grid;
  gap: 28px;
}

.page-about .service-copy > p {
  margin: 18px 0 0;
  max-width: 34em;
  font-size: 16px;
  line-height: 1.8;
  color: var(--text-dim);
}

.page-about .service-facts {
  margin: 26px 0 0;
  display: grid;
  gap: 0;
  border-top: 1px solid var(--line);
}

.page-about .service-facts__row {
  display: grid;
  grid-template-columns: 90px minmax(0, 1fr);
  gap: 12px;
  padding-block: 12px;
  border-bottom: 1px solid var(--line);
}

.page-about .service-facts dt {
  font-size: 13px;
  color: var(--muted);
}

.page-about .service-facts dd {
  margin: 0;
  font-size: 14.5px;
  line-height: 1.65;
  color: var(--text);
}

.page-about .service-card {
  padding: 22px 18px;
}

.page-about .service-card__label {
  margin: 0;
  font-size: 12px;
  letter-spacing: 0.12em;
  color: var(--cyan);
}

.page-about .service-card__mail {
  margin: 14px 0 12px;
  font-size: 14px;
  line-height: 1.5;
  color: var(--text);
  word-break: break-all;
}

.page-about .service-card__phone {
  margin: 18px 0 0;
  font-size: 20px;
  letter-spacing: 0.04em;
  color: var(--cyan-hi);
}

.page-about .service-card__note {
  margin: 12px 0 20px;
  font-size: 13px;
  line-height: 1.75;
  color: var(--muted);
}

/* ---------- 断点 ---------- */

@media (min-width: 640px) {
  .page-about .about-hero__lead {
    font-size: 17px;
  }

  .page-about .stage {
    padding: 24px 24px 26px;
  }
}

@media (min-width: 900px) {
  .page-about .about-hero__grid {
    grid-template-columns: minmax(0, 1fr) 296px;
    gap: clamp(32px, 5vw, 72px);
    align-items: start;
  }

  .page-about .about-hero__side {
    padding-top: 46px;
  }

  .page-about .origin-grid {
    grid-template-columns: minmax(0, 1.12fr) minmax(0, 0.88fr);
    gap: clamp(32px, 5vw, 72px);
    align-items: start;
  }

  .page-about .origin-shot {
    margin-top: 8px;
  }

  .page-about .v4-grid {
    grid-template-columns: minmax(0, 1fr) minmax(0, 0.82fr);
    gap: clamp(32px, 5vw, 68px);
    align-items: start;
  }

  .page-about .maint-grid {
    grid-template-columns: minmax(0, 1.1fr) minmax(0, 0.9fr);
    gap: clamp(28px, 4vw, 56px);
    align-items: start;
  }

  .page-about .service-grid {
    grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr);
    gap: clamp(28px, 4vw, 60px);
    align-items: start;
  }

  .page-about .service-card {
    padding: 26px 24px;
  }

  /* 时间轴切换为左侧纵向轨道 */
  .page-about .tl {
    grid-template-columns: 190px minmax(0, 1fr);
    gap: clamp(30px, 4vw, 60px);
    align-items: start;
  }

  .page-about .tl__rail {
    position: sticky;
    top: calc(var(--header-h) + 28px);
    flex-direction: column;
    gap: 0;
    overflow: visible;
    padding: 0;
  }

  .page-about .tl__rail::before {
    content: "";
    position: absolute;
    left: 6px;
    top: 18px;
    bottom: 18px;
    width: 1px;
    background: var(--line);
  }

  .page-about .tl__rail li {
    padding: 11px 0;
    border: 0;
    background: none;
  }

  .page-about .tl__rail li::before {
    position: relative;
    z-index: 1;
  }

  .page-about .tl__rail li[data-active="true"] {
    border-color: transparent;
  }

  .page-about .tl__rail a {
    font-size: 12.5px;
  }

  /* 阶段卡片错位排布 */
  .page-about .stage {
    padding: 26px 28px 28px;
  }

  .page-about .stage:nth-child(odd) {
    margin-right: 11%;
  }

  .page-about .stage:nth-child(even) {
    margin-left: 11%;
  }

  .page-about .stage + .stage {
    margin-top: 26px;
  }

  .page-about .stage h3 {
    font-size: 21px;
  }
}

@media (min-width: 1200px) {
  .page-about .about-hero__grid {
    grid-template-columns: minmax(0, 1fr) 320px;
  }

  .page-about .tl {
    grid-template-columns: 210px minmax(0, 1fr);
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .tl__rail a,
  .page-about .breadcrumbs__list a {
    transition: none;
  }
}