/* ===== 品牌与价值 · 页面专属样式（作用域 .page-about） ===== */

.page-about {
  background: var(--ink);
  color: var(--text);
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  position: relative;
  padding: clamp(18px, 4vw, 40px) 0 clamp(26px, 4vw, 48px);
  border-bottom: 1px solid var(--line);
}

.page-about .about-hero::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 7px;
  background: repeating-linear-gradient(90deg, var(--line) 0 1px, transparent 1px 14px);
  opacity: .85;
  pointer-events: none;
}

.page-about .hero-title {
  font-family: var(--font-display);
  font-size: clamp(34px, 7.4vw, 88px);
  font-weight: 800;
  line-height: 1.04;
  letter-spacing: .005em;
  margin: 14px 0 18px;
  max-width: 900px;
  word-break: break-word;
}

.page-about .hero-lede {
  font-size: clamp(16px, 1.5vw, 20px);
  line-height: 1.78;
  color: var(--text);
  max-width: 62ch;
  margin: 0;
}

.page-about .hero-stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px 12px;
  margin: 30px 0 0;
  padding: 0;
}

.page-about .hero-stats > div {
  min-width: 0;
  border-left: 2px solid var(--line);
  padding-left: 12px;
}

.page-about .hero-stats > div:first-child {
  border-left-color: var(--gold);
}

.page-about .hero-stats dt {
  font-size: 12px;
  letter-spacing: .1em;
  color: var(--cold);
  margin: 0;
}

.page-about .hero-stats dd {
  margin: 6px 0 0;
  font-size: 20px;
  color: var(--text);
}

.page-about .hero-stats .stat-num {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 26px;
  color: var(--cyan);
  margin-right: 2px;
}

.page-about .hero-stats > div:first-child .stat-num {
  color: var(--gold);
}

/* ---------- 主体骨架：左窄栏 + 右弹性栏 ---------- */
.page-about .about-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 36px;
  padding: clamp(28px, 5vw, 64px) 0 clamp(48px, 7vw, 96px);
}

.page-about .about-rail {
  align-self: start;
  min-width: 0;
}

.page-about .rail-label {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .16em;
  color: var(--cold);
  margin: 0 0 12px;
  text-transform: uppercase;
}

.page-about .rail-list {
  list-style: none;
  margin: 0;
  padding: 0;
  border-left: 1px solid var(--line);
}

.page-about .rail-link {
  display: block;
  padding: 9px 0 9px 16px;
  margin-left: -1px;
  border-left: 2px solid transparent;
  color: var(--cold);
  font-size: 14px;
  line-height: 1.5;
  text-decoration: none;
  transition: color .18s var(--ease), border-color .18s var(--ease);
}

.page-about .rail-link:hover,
.page-about .rail-link:focus-visible {
  color: var(--text);
}

.page-about .rail-link.is-active,
.page-about .rail-link[aria-current] {
  color: var(--cyan);
  border-left-color: var(--cyan);
}

.page-about .about-body {
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: clamp(48px, 7vw, 88px);
}

/* ---------- 章节通用 ---------- */
.page-about .about-section {
  min-width: 0;
}

.page-about .about-head {
  margin: 0 0 22px;
}

.page-about .about-section .section-index {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .18em;
  color: var(--gold);
  margin: 0 0 8px;
}

.page-about .about-section .section-title {
  font-family: var(--font-display);
  font-size: clamp(26px, 4.4vw, 44px);
  font-weight: 800;
  line-height: 1.14;
  margin: 0;
  max-width: 26ch;
}

.page-about .about-copy {
  min-width: 0;
}

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

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

.page-about .about-copy a {
  color: var(--cyan);
  text-underline-offset: 3px;
}

.page-about .about-grid {
  display: grid;
  gap: 22px;
  margin-bottom: 26px;
}

.page-about .media-frame img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
}

/* ---------- 三级流程卡片 ---------- */
.page-about .check-list {
  display: grid;
  gap: 10px;
}

.page-about .check-card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--char);
  overflow: hidden;
}

.page-about .check-card[open] {
  border-color: var(--deep-cyan);
  background: var(--lift);
}

.page-about .check-card summary {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px;
  cursor: pointer;
  list-style: none;
}

.page-about .check-card summary::-webkit-details-marker {
  display: none;
}

.page-about .check-card summary:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: -2px;
}

.page-about .check-step {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 13px;
  color: var(--gold);
}

.page-about .check-name {
  font-size: 15px;
  font-weight: 600;
  color: var(--text);
  flex: 1 1 auto;
  min-width: 0;
}

.page-about .check-card summary::after {
  content: "+";
  font-family: var(--font-mono);
  font-size: 16px;
  color: var(--cyan);
  line-height: 1;
}

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

.page-about .check-card p {
  margin: 0;
  padding: 0 16px 18px;
  font-size: 14px;
  line-height: 1.8;
  color: var(--cold);
}

/* ---------- 多联赛分栏 · 数据行 ---------- */
.page-about .split-stats {
  display: grid;
  gap: 16px;
  list-style: none;
  margin: 28px 0 0;
  padding: 0;
}

.page-about .split-stats li {
  min-width: 0;
  border-top: 1px solid var(--line);
  padding-top: 14px;
}

.page-about .stat-line {
  margin: 0;
  display: flex;
  align-items: baseline;
  gap: 4px;
}

.page-about .stat-num {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 30px;
  line-height: 1.1;
  color: var(--cyan);
  letter-spacing: -.01em;
}

.page-about .split-stats li:first-child .stat-num {
  color: var(--cold);
}

.page-about .split-stats li:nth-child(2) .stat-num {
  color: var(--gold);
}

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

.page-about .stat-label {
  margin: 8px 0 0;
  font-size: 13px;
  line-height: 1.7;
  color: var(--cold);
}

/* ---------- 版本演进时间轴 ---------- */
.page-about .tl {
  position: relative;
  list-style: none;
  margin: 30px 0 0;
  padding: 0;
}

.page-about .tl::before {
  content: "";
  position: absolute;
  left: 7px;
  top: 8px;
  bottom: 10px;
  width: 1px;
  background: linear-gradient(180deg, var(--cyan) 0%, var(--line) 60%, var(--line) 100%);
}

.page-about .tl-item {
  position: relative;
  padding: 0 0 32px 36px;
  min-width: 0;
}

.page-about .tl-item:last-child {
  padding-bottom: 0;
}

.page-about .tl-node {
  position: absolute;
  left: 0;
  top: 5px;
  width: 15px;
  height: 15px;
  border-radius: 50%;
  border: 1px solid var(--line);
  background: var(--ink);
}

.page-about .tl-item:last-child .tl-node {
  border-color: var(--gold);
  background: var(--gold);
  box-shadow: 0 0 0 5px rgba(255, 158, 61, .16);
}

.page-about .tl-ver {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 13px;
  letter-spacing: .06em;
  color: var(--cyan);
  margin: 0 0 6px;
}

.page-about .tl-title {
  font-family: var(--font-display);
  font-size: clamp(20px, 2.4vw, 26px);
  font-weight: 700;
  line-height: 1.2;
  margin: 0 0 8px;
  color: var(--text);
}

.page-about .tl-text {
  margin: 0;
  font-size: 15px;
  line-height: 1.78;
  color: var(--cold);
  max-width: 62ch;
}

/* ---------- 值班与响应 ---------- */
.page-about .oncall-band {
  display: grid;
  gap: 20px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: linear-gradient(165deg, var(--char) 0%, var(--ink) 78%);
  padding: clamp(18px, 3vw, 30px);
}

.page-about .oncall-band .about-copy p {
  color: var(--text);
}

/* ---------- 合规与资质 ---------- */
.page-about .tag-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  list-style: none;
  margin: 24px 0 18px;
  padding: 0;
}

.page-about .note a {
  color: var(--cyan);
  text-underline-offset: 3px;
}

/* ---------- 为什么选择天博 ---------- */
.page-about .why-grid {
  display: grid;
  gap: 20px;
}

.page-about .why-card {
  min-width: 0;
  border-top: 2px solid var(--cyan);
  padding-top: 16px;
}

.page-about .why-card:nth-child(2) {
  border-top-color: var(--gold);
}

.page-about .why-card:nth-child(3) {
  border-top-color: var(--line);
}

.page-about .why-card h3 {
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 700;
  letter-spacing: .01em;
  margin: 0 0 10px;
  color: var(--text);
}

.page-about .why-card p {
  margin: 0;
  font-size: 15px;
  line-height: 1.78;
  color: var(--cold);
}

.page-about .cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 30px;
}

.page-about .cta-row .btn {
  text-decoration: none;
}

.page-about .about-section #why .note,
.page-about #why .note {
  margin-top: 18px;
}

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

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

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

@media (min-width: 820px) {
  .page-about .about-grid {
    grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr);
    gap: 32px;
    align-items: start;
  }

  .page-about .check-list {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    align-items: start;
  }

  .page-about .why-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 24px;
  }

  .page-about .oncall-band {
    grid-template-columns: minmax(0, 1.05fr) minmax(0, 1fr);
    align-items: center;
    gap: 34px;
  }
}

@media (min-width: 1000px) {
  .page-about .about-layout {
    grid-template-columns: 288px minmax(0, 1fr);
    gap: 72px;
  }

  .page-about .about-rail {
    position: sticky;
    top: calc(var(--header-h) + 28px);
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .rail-link {
    transition: none;
  }
}