.page-about {
  --about-rail: 200px;
  --about-top: 100px;
}

.page-about .about-hero {
  padding: 36px 0 44px;
  border-bottom: 1px solid var(--line);
}

.page-about .breadcrumb {
  margin-bottom: 26px;
}

.page-about .about-hero .eyebrow {
  margin: 0 0 16px;
  font-size: 11.5px;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--slate);
}

.page-about .about-hero h1 {
  margin: 0 0 24px;
  font-size: clamp(2.1rem, 6.6vw, 3.5rem);
  font-weight: 900;
  line-height: 1.1;
  letter-spacing: -.02em;
  color: var(--ink);
  max-width: 15em;
}

.page-about .about-lead {
  margin: 0;
  max-width: 60ch;
  padding-left: 16px;
  border-left: 2px solid var(--orange);
  font-size: 1.0625rem;
  line-height: 1.8;
  color: var(--ink-2);
}

/* ---------- 双栏骨架 ---------- */
.page-about .about-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 32px;
  padding-top: 36px;
  padding-bottom: 64px;
}

@media (min-width: 900px) {
  .page-about .about-layout {
    grid-template-columns: var(--about-rail) minmax(0, 1fr);
    gap: 52px;
    padding-top: 52px;
    padding-bottom: 88px;
  }
}

/* ---------- 侧栏 ---------- */
.page-about .about-rail {
  display: flex;
  flex-wrap: wrap;
  gap: 24px 36px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--line);
}

@media (min-width: 900px) {
  .page-about .about-rail {
    display: block;
    position: sticky;
    top: var(--about-top);
    align-self: start;
    padding: 0 0 0 18px;
    border-bottom: 0;
    border-left: 1px solid var(--line);
  }
}

.page-about .rail-block + .rail-block {
  margin-top: 0;
}

@media (min-width: 900px) {
  .page-about .rail-block + .rail-block {
    margin-top: 30px;
  }
}

.page-about .rail-label {
  margin: 0 0 12px;
  font-size: 11px;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--slate);
}

.page-about .rail-nav,
.page-about .rail-years {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .rail-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 4px 18px;
}

@media (min-width: 900px) {
  .page-about .rail-nav {
    display: block;
  }
}

.page-about .rail-nav li {
  margin: 0;
}

.page-about .rail-nav a {
  display: flex;
  align-items: baseline;
  gap: 8px;
  padding: 4px 0;
  font-size: 14px;
  color: var(--ink-2);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color 160ms var(--ease), border-color 160ms var(--ease);
}

.page-about .rail-nav a .mono {
  font-size: 11px;
  color: var(--slate);
  transition: color 160ms var(--ease);
}

.page-about .rail-nav a:hover {
  color: var(--orange-deep);
  border-bottom-color: var(--orange);
}

.page-about .rail-nav a:hover .mono {
  color: var(--orange-deep);
}

.page-about .rail-years {
  display: flex;
  gap: 20px;
}

@media (min-width: 900px) {
  .page-about .rail-years {
    display: block;
    position: relative;
    padding-left: 0;
  }

  .page-about .rail-years::before {
    content: "";
    position: absolute;
    left: 3px;
    top: 10px;
    bottom: 10px;
    width: 1px;
    background: var(--line-strong);
  }
}

.page-about .rail-years li {
  margin: 0;
}

.page-about .rail-years a {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 4px 0;
  font-size: 13px;
  color: var(--slate);
  text-decoration: none;
  transition: color 160ms var(--ease);
}

.page-about .rail-dot {
  flex: 0 0 auto;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--orange);
  box-shadow: 0 0 0 3px var(--orange-soft);
  transition: transform 160ms var(--ease);
}

.page-about .rail-years a:hover {
  color: var(--orange-deep);
}

.page-about .rail-years a:hover .rail-dot {
  transform: scale(1.5);
}

/* ---------- 叙事栏 ---------- */
.page-about .about-story {
  min-width: 0;
  display: flex;
  flex-direction: column;
}

.page-about .about-chapter {
  padding-top: 36px;
  padding-bottom: 36px;
  border-top: 1px solid var(--line);
}

.page-about .about-chapter:first-child {
  padding-top: 0;
  border-top: 0;
}

@media (min-width: 900px) {
  .page-about .about-chapter {
    padding-top: 48px;
    padding-bottom: 48px;
  }
}

.page-about .about-chapter,
.page-about .milestone-list > li {
  scroll-margin-top: 96px;
}

.page-about .chapter-tag {
  display: flex;
  align-items: center;
  gap: 12px;
  margin: 0 0 14px;
  font-size: 11.5px;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--slate);
}

.page-about .chapter-tag::after {
  content: "";
  flex: 1;
  max-width: 120px;
  height: 1px;
  background: var(--line-strong);
}

.page-about .about-chapter h2 {
  margin: 0 0 20px;
  font-size: clamp(1.3rem, 3.2vw, 1.8rem);
  font-weight: 700;
  line-height: 1.3;
  letter-spacing: -.01em;
  color: var(--ink);
  max-width: 24em;
}

.page-about .prose p {
  margin: 0 0 16px;
  font-size: 1.0625rem;
  line-height: 1.82;
  color: var(--ink-2);
  max-width: 40em;
}

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

.page-about .prose a {
  color: var(--orange-deep);
  text-decoration: none;
  border-bottom: 1px solid currentColor;
  transition: border-bottom-width 160ms var(--ease);
}

.page-about .prose a:hover {
  border-bottom-width: 2px;
}

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

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

.page-about .about-figure--side {
  margin-top: 0;
}

/* ---------- 伙伴四栏 ---------- */
.page-about .partner-grid {
  list-style: none;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1px;
  margin: 26px 0 0;
  padding: 0;
  background: var(--line-strong);
  border: 1px solid var(--line-strong);
}

@media (min-width: 600px) {
  .page-about .partner-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (min-width: 1080px) {
  .page-about .partner-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

.page-about .partner-grid li {
  background: var(--white);
  padding: 20px 18px 22px;
}

.page-about .partner-name {
  margin: 0 0 10px;
  font-size: 12px;
  letter-spacing: .12em;
  color: var(--orange-deep);
}

.page-about .partner-desc {
  margin: 0;
  font-size: 15px;
  line-height: 1.7;
  color: var(--ink-2);
}

/* ---------- 客户区 ---------- */
.page-about .client-split {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 28px;
  align-items: start;
}

@media (min-width: 860px) {
  .page-about .client-split {
    grid-template-columns: minmax(0, 1.05fr) minmax(0, 0.85fr);
    gap: 40px;
  }
}

/* ---------- 五步折叠 ---------- */
.page-about .step-list {
  list-style: none;
  margin: 26px 0 0;
  padding: 0;
  border-top: 1px solid var(--line-strong);
}

.page-about .step-list li {
  margin: 0;
  border-bottom: 1px solid var(--line);
}

.page-about .step-list summary {
  display: flex;
  align-items: baseline;
  gap: 14px;
  padding: 16px 6px;
  cursor: pointer;
  list-style: none;
  transition: background-color 160ms var(--ease);
}

.page-about .step-list summary::-webkit-details-marker {
  display: none;
}

.page-about .step-list summary:hover {
  background: var(--orange-soft);
}

.page-about .step-list summary::after {
  content: "+";
  margin-left: auto;
  font-family: var(--mono);
  font-size: 15px;
  line-height: 1;
  color: var(--slate);
}

.page-about .step-list details[open] summary::after {
  content: "−";
  color: var(--orange-deep);
}

.page-about .step-no {
  font-size: 11.5px;
  letter-spacing: .1em;
  color: var(--orange-deep);
}

.page-about .step-name {
  font-size: 16px;
  font-weight: 700;
  color: var(--ink);
}

.page-about .step-body {
  padding: 6px 6px 22px 44px;
  font-size: 15px;
  line-height: 1.75;
  color: var(--ink-2);
}

.page-about .step-body p {
  margin: 0 0 10px;
}

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

.page-about .step-body strong {
  display: block;
  margin-bottom: 2px;
  font-family: var(--mono);
  font-size: 11px;
  font-weight: 400;
  letter-spacing: .14em;
  color: var(--slate);
}

/* ---------- 三道校验 ---------- */
.page-about .check-list {
  list-style: none;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1px;
  margin: 24px 0 26px;
  padding: 0;
  background: var(--line-strong);
  border: 1px solid var(--line-strong);
}

@media (min-width: 760px) {
  .page-about .check-list {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

.page-about .check-list li {
  margin: 0;
  background: var(--white);
  padding: 20px 18px 22px;
}

.page-about .check-name {
  margin: 0 0 10px;
  font-size: 12px;
  letter-spacing: .1em;
  color: var(--orange-deep);
}

.page-about .check-desc {
  margin: 0;
  font-size: 15px;
  line-height: 1.7;
  color: var(--ink-2);
}

/* ---------- 年表 ---------- */
.page-about .milestone-list {
  list-style: none;
  margin: 26px 0 0;
  padding: 0 0 0 0;
  border-left: 1px solid var(--line-strong);
}

.page-about .milestone-list > li {
  position: relative;
  padding: 0 0 30px 26px;
}

.page-about .milestone-list > li:last-child {
  padding-bottom: 0;
}

.page-about .milestone-list > li::before {
  content: "";
  position: absolute;
  left: -4px;
  top: 6px;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--white);
  border: 1px solid var(--slate);
  transition: background-color 160ms var(--ease), border-color 160ms var(--ease);
}

.page-about .milestone-list > li:target::before {
  background: var(--orange);
  border-color: var(--orange);
  box-shadow: 0 0 0 4px var(--orange-soft);
}

.page-about .mile-year {
  margin: 0 0 8px;
  font-size: 12.5px;
  letter-spacing: .14em;
  color: var(--slate);
}

.page-about .milestone-list > li:target .mile-year {
  color: var(--orange-deep);
}

.page-about .milestone-list h3 {
  margin: 0 0 10px;
  font-size: 1.0625rem;
  font-weight: 700;
  line-height: 1.4;
  color: var(--ink);
}

.page-about .milestone-list p {
  margin: 0;
  font-size: 15.5px;
  line-height: 1.8;
  color: var(--ink-2);
  max-width: 38em;
}

.page-about .milestone-list a {
  color: var(--orange-deep);
  text-decoration: none;
  border-bottom: 1px solid currentColor;
}

.page-about .milestone-list a:hover {
  border-bottom-width: 2px;
}

/* ---------- 收尾 ---------- */
.page-about .about-cta {
  background: var(--ink);
  color: var(--on-dark);
  padding: 56px 0 64px;
}

.page-about .cta-panel {
  max-width: 720px;
}

.page-about .cta-label {
  margin: 0 0 16px;
  font-size: 11.5px;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--orange);
}

.page-about .cta-panel h2 {
  margin: 0 0 18px;
  font-size: clamp(1.4rem, 3.4vw, 2rem);
  font-weight: 900;
  line-height: 1.28;
  letter-spacing: -.01em;
  color: var(--on-dark);
}

.page-about .cta-panel p {
  margin: 0 0 26px;
  font-size: 1rem;
  line-height: 1.8;
  color: rgba(237, 234, 228, .76);
  max-width: 44em;
}

.page-about .cta-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.page-about .about-cta .btn--ghost {
  color: var(--on-dark);
  border-color: rgba(237, 234, 228, .38);
}

.page-about .about-cta .btn--ghost:hover {
  border-color: var(--orange);
  color: var(--orange);
}

@media (prefers-reduced-motion: reduce) {
  .page-about *,
  .page-about *::before,
  .page-about *::after {
    transition-duration: .01ms !important;
    animation-duration: .01ms !important;
    scroll-behavior: auto !important;
  }
}