.page-about {
  --about-rail-w: 172px;
}

/* ===== 首屏 ===== */
.page-about .about-hero {
  position: relative;
  overflow: hidden;
  padding-block: clamp(2.25rem, 5.5vw, 4.25rem) clamp(1.75rem, 4vw, 3rem);
  border-bottom: 1px solid var(--grid);
}

.page-about .about-hero::before {
  content: "";
  position: absolute;
  top: -30%;
  right: -12%;
  width: min(620px, 78%);
  height: 160%;
  background-image:
    linear-gradient(90deg, var(--grid) 1px, transparent 1px),
    linear-gradient(180deg, var(--grid) 1px, transparent 1px);
  background-size: 42px 42px;
  opacity: .55;
  -webkit-mask-image: radial-gradient(closest-side, #000 15%, transparent 82%);
  mask-image: radial-gradient(closest-side, #000 15%, transparent 82%);
  pointer-events: none;
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  left: clamp(1rem, 4vw, 3rem);
  bottom: 14%;
  width: min(220px, 26%);
  height: 1px;
  background: linear-gradient(90deg, var(--cyan-a34), transparent);
  transform: rotate(-7deg);
  transform-origin: left center;
  pointer-events: none;
}

.page-about .about-hero .container {
  position: relative;
  z-index: 1;
}

.page-about .about-crumb {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: .5rem;
  margin-bottom: clamp(1.25rem, 3vw, 2rem);
  font-size: .8125rem;
  color: var(--muted);
}

.page-about .about-crumb a {
  color: var(--muted);
  text-decoration: none;
  border-bottom: 1px solid var(--grid);
  transition: color .18s ease, border-color .18s ease;
}

.page-about .about-crumb a:hover,
.page-about .about-crumb a:focus-visible {
  color: var(--cyan);
  border-bottom-color: var(--cyan);
}

.page-about .about-crumb span[aria-current] {
  color: var(--ink);
}

.page-about .hero-grid {
  display: grid;
  gap: clamp(1.5rem, 3.5vw, 2.75rem);
}

.page-about .hero-mark {
  display: block;
  width: 62px;
  height: 3px;
  margin-bottom: 1.15rem;
  background: var(--cyan);
}

.page-about .about-hero h1 {
  margin: 0;
  max-width: 18ch;
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(1.85rem, 7vw, 3.35rem);
  line-height: 1.08;
  letter-spacing: -.02em;
  color: var(--ink);
}

.page-about .about-hero__lead {
  margin: 0 0 clamp(1.25rem, 3vw, 1.75rem);
  max-width: 34rem;
  font-size: clamp(.9375rem, 1.5vw, 1.0625rem);
  line-height: 1.8;
  color: var(--body-ink);
}

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

.page-about .hero-stats > div {
  padding: .8rem .95rem;
  background: var(--console);
}

.page-about .hero-stats dt {
  font-size: .75rem;
  letter-spacing: .02em;
  color: var(--muted);
}

.page-about .hero-stats dd {
  margin: .35rem 0 0;
  font-family: var(--font-mono);
  font-size: 1.1rem;
  font-weight: 600;
  letter-spacing: .04em;
  color: var(--cyan-bright);
}

/* ===== 左轴 + 右栏长卷 ===== */
.page-about .about-scroll {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(1.5rem, 4vw, 3rem);
  padding-block: clamp(1.75rem, 4vw, 3rem) clamp(3rem, 7vw, 5.5rem);
}

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

.page-about .about-rail__cap {
  margin: 0 0 .75rem;
  font-size: .6875rem;
  letter-spacing: .2em;
  text-transform: uppercase;
  color: var(--steel);
}

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

.page-about .rail-node {
  display: grid;
  grid-template-columns: 2.1rem minmax(0, 1fr);
  align-items: baseline;
  gap: .5rem;
  margin-left: -1px;
  padding: .7rem .6rem .7rem .85rem;
  border-left: 1px solid var(--grid);
  font-size: .8125rem;
  color: var(--muted);
  text-decoration: none;
  transition: color .18s ease, background-color .18s ease, border-color .18s ease;
}

.page-about .rail-node__num {
  font-size: .6875rem;
  letter-spacing: .1em;
  color: var(--steel);
  transition: color .18s ease;
}

.page-about .rail-node:hover,
.page-about .rail-node:focus-visible {
  border-left-color: var(--cyan);
  background: var(--cyan-a08);
  color: var(--ink);
}

.page-about .rail-node:hover .rail-node__num,
.page-about .rail-node:focus-visible .rail-node__num {
  color: var(--cyan);
}

/* ===== 章节骨架 ===== */
.page-about .about-section {
  padding-block: clamp(1.9rem, 4.4vw, 3.25rem);
  border-top: 1px solid var(--grid);
  scroll-margin-top: 1.5rem;
}

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

.page-about .about-head {
  display: grid;
  gap: .4rem;
  margin-bottom: 1.1rem;
}

.page-about .about-head__num {
  font-size: .6875rem;
  letter-spacing: .22em;
  color: var(--cyan);
}

.page-about .about-head h2 {
  margin: 0;
  max-width: 24ch;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(1.3rem, 3.6vw, 1.9rem);
  line-height: 1.22;
  letter-spacing: -.015em;
  color: var(--ink);
}

.page-about .about-lead {
  margin: 0 0 clamp(1.15rem, 2.6vw, 1.6rem);
  max-width: 38rem;
  font-size: 1rem;
  line-height: 1.8;
  color: var(--body-ink);
}

/* ===== 图片 ===== */
.page-about .about-figure {
  margin: 0 0 clamp(1.25rem, 3vw, 1.75rem);
}

.page-about .about-figure img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  border: 1px solid var(--grid);
  background: var(--console);
}

.page-about .about-figure figcaption {
  margin-top: .6rem;
  font-size: .75rem;
  letter-spacing: .06em;
  color: var(--muted);
}

/* ===== 01 三类问题 ===== */
.page-about .issue-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .issue {
  padding: 1.05rem 1rem;
  border-left: 2px solid var(--grid);
  transition: background-color .2s ease, border-color .2s ease;
}

.page-about .issue + .issue {
  border-top: 1px solid var(--grid);
}

.page-about .issue:hover {
  border-left-color: var(--cyan);
  background: var(--cyan-a08);
}

.page-about .issue h3 {
  margin: 0 0 .3rem;
  font-family: var(--font-display);
  font-size: 1.0625rem;
  font-weight: 700;
  letter-spacing: -.01em;
  color: var(--ink);
}

.page-about .issue p {
  margin: 0;
  max-width: 40rem;
  font-size: .9375rem;
  line-height: 1.78;
  color: var(--body-ink);
}

/* ===== 02 发展历程 ===== */
.page-about .era-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .era {
  display: grid;
  gap: .5rem;
  padding: 1.1rem 0 1.1rem 1rem;
  border-top: 1px solid var(--grid);
  border-left: 2px solid var(--grid);
  transition: border-color .2s ease, background-color .2s ease;
}

.page-about .era:hover {
  background: var(--cyan-a08);
  border-left-color: var(--cyan);
}

.page-about .era:nth-child(1) { opacity: .78; }
.page-about .era:nth-child(2) { opacity: .86; }
.page-about .era:nth-child(3) { opacity: .94; }
.page-about .era:nth-child(4) { opacity: 1; }

.page-about .era:nth-child(2) { border-left-color: var(--steel); }
.page-about .era:nth-child(3) { border-left-color: var(--violet); }
.page-about .era:nth-child(4) { border-left-color: var(--cyan); }

.page-about .era__when {
  font-size: .75rem;
  letter-spacing: .1em;
  color: var(--muted);
}

.page-about .era__body h3 {
  margin: 0 0 .3rem;
  font-family: var(--font-display);
  font-size: 1.0625rem;
  font-weight: 700;
  letter-spacing: -.01em;
  color: var(--ink);
}

.page-about .era__body p {
  margin: 0;
  max-width: 40rem;
  font-size: .9375rem;
  line-height: 1.78;
  color: var(--body-ink);
}

/* ===== 03 团队分工 ===== */
.page-about .role-grid {
  display: grid;
  gap: 1px;
  background: var(--grid);
  border: 1px solid var(--grid);
}

.page-about .role {
  display: grid;
  align-content: start;
  gap: .45rem;
  padding: clamp(1.05rem, 2.4vw, 1.5rem);
  border-top: 2px solid var(--grid);
  background: var(--console);
  transition: background-color .2s ease, border-color .2s ease;
}

.page-about .role:hover {
  border-top-color: var(--cyan);
  background: var(--cyan-a08);
}

.page-about .role__num {
  font-size: .75rem;
  letter-spacing: .18em;
  color: var(--cyan);
}

.page-about .role h3 {
  margin: 0;
  font-family: var(--font-display);
  font-size: 1.1rem;
  font-weight: 800;
  letter-spacing: -.01em;
  color: var(--ink);
}

.page-about .role p {
  margin: 0;
  font-size: .9375rem;
  line-height: 1.78;
  color: var(--body-ink);
}

/* ===== 04 服务标准 ===== */
.page-about .std-grid {
  display: grid;
  gap: clamp(1.25rem, 3vw, 2rem);
}

.page-about .std-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .std-list li {
  display: grid;
  gap: .3rem;
  padding: .9rem 0;
  border-top: 1px solid var(--grid);
}

.page-about .std-list li:last-child {
  border-bottom: 1px solid var(--grid);
}

.page-about .std-key {
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: .02em;
  color: var(--cyan-bright);
}

.page-about .std-desc {
  max-width: 34rem;
  font-size: .9375rem;
  line-height: 1.75;
  color: var(--body-ink);
}

.page-about .std-note {
  margin: 1rem 0 0;
  max-width: 34rem;
  font-size: .875rem;
  line-height: 1.75;
  color: var(--muted);
}

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

/* ===== 05 更新节奏 ===== */
.page-about .pulse-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: var(--gap);
}

.page-about .pulse {
  display: grid;
  align-content: start;
  gap: .55rem;
  padding: clamp(1.05rem, 2.4vw, 1.4rem);
  border: 1px solid var(--grid);
  background: var(--console);
  transition: border-color .2s ease, background-color .2s ease;
}

.page-about .pulse:hover {
  border-color: var(--cyan-a34);
  background: var(--cyan-a08);
}

.page-about .pulse__tag {
  justify-self: start;
  font-size: .6875rem;
  letter-spacing: .12em;
}

.page-about .pulse h3 {
  margin: 0;
  font-family: var(--font-display);
  font-size: 1.05rem;
  font-weight: 700;
  letter-spacing: -.01em;
  color: var(--ink);
}

.page-about .pulse p {
  margin: 0;
  font-size: .9375rem;
  line-height: 1.78;
  color: var(--body-ink);
}

.page-about .pulse__link {
  justify-self: start;
  margin-top: .15rem;
  font-size: .8125rem;
  letter-spacing: .04em;
  color: var(--cyan);
  text-decoration: none;
  border-bottom: 1px solid var(--cyan-a34);
  padding-bottom: 2px;
  transition: border-color .2s ease, color .2s ease;
}

.page-about .pulse__link:hover,
.page-about .pulse__link:focus-visible {
  color: var(--cyan-bright);
  border-bottom-color: var(--cyan);
}

/* ===== 收尾 ===== */
.page-about .about-cta {
  display: grid;
  gap: 1rem;
  margin-top: clamp(1.5rem, 3.5vw, 2.25rem);
  padding: clamp(1.2rem, 3vw, 1.9rem);
  border: 1px solid var(--grid);
  background: linear-gradient(135deg, var(--cyan-a08), transparent 62%);
}

.page-about .about-cta__text {
  margin: 0;
  max-width: 34rem;
  font-size: .9375rem;
  line-height: 1.78;
  color: var(--body-ink);
}

.page-about .about-cta__actions {
  display: flex;
  flex-wrap: wrap;
  gap: .65rem;
}

/* ===== 响应式 ===== */
@media (min-width: 620px) {
  .page-about .std-list li {
    grid-template-columns: 7.5rem minmax(0, 1fr);
    align-items: baseline;
    gap: 1rem;
  }
}

@media (min-width: 760px) {
  .page-about .hero-stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

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

  .page-about .about-cta {
    grid-template-columns: minmax(0, 1fr) auto;
    align-items: center;
  }
}

@media (min-width: 900px) {
  .page-about .hero-grid {
    grid-template-columns: minmax(0, 1.05fr) minmax(0, .95fr);
    align-items: end;
  }

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

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

@media (min-width: 960px) {
  .page-about .about-scroll {
    grid-template-columns: var(--about-rail-w) minmax(0, 1fr);
    align-items: start;
  }

  .page-about .about-rail {
    position: sticky;
    top: 1.5rem;
  }
}

@media (max-width: 959px) {
  .page-about .about-rail__cap {
    display: none;
  }

  .page-about .rail-track {
    display: flex;
    gap: .5rem;
    padding-bottom: .5rem;
    border-left: 0;
    overflow-x: auto;
    scrollbar-width: thin;
  }

  .page-about .rail-track > li {
    flex: 0 0 auto;
  }

  .page-about .rail-node {
    grid-template-columns: auto auto;
    gap: .4rem;
    margin-left: 0;
    padding: .5rem .7rem;
    border: 1px solid var(--grid);
    white-space: nowrap;
  }
}

@media (max-width: 479px) {
  .page-about .hero-stats {
    grid-template-columns: minmax(0, 1fr);
  }

  .page-about .about-figure figcaption {
    font-size: .6875rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .rail-node,
  .page-about .issue,
  .page-about .era,
  .page-about .role,
  .page-about .pulse,
  .page-about .pulse__link,
  .page-about .about-crumb a {
    transition: none;
  }
}
<<<END>>>