.page-about {
  --about-rail: 236px;
  --about-gutter: 56px;
  --about-line: rgba(124, 143, 138, 0.28);
  --about-line-soft: rgba(124, 143, 138, 0.16);
  padding-bottom: 72px;
}

/* ---------- 首屏 ---------- */
.page-about .about-wrap {
  padding-top: 8px;
}

.page-about .about-hero {
  position: relative;
  margin-top: 18px;
  padding: 36px 0 0;
  background:
    radial-gradient(90% 70% at 4% 0%, rgba(20, 86, 78, 0.6), transparent 60%),
    linear-gradient(180deg, rgba(14, 46, 42, 0.55), rgba(11, 31, 26, 0) 72%);
}

.page-about .about-hero__title {
  font-family: var(--sans);
  font-weight: 800;
  font-size: clamp(30px, 6vw, 62px);
  line-height: 1.15;
  letter-spacing: -0.035em;
  color: var(--white);
  margin: 16px 0 24px;
  max-width: 17em;
}

.page-about .about-hero__lede {
  font-family: var(--serif);
  font-size: 17px;
  line-height: 1.9;
  color: var(--paper);
  margin: 0;
  max-width: 36em;
}

.page-about .about-hero__facts {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px 22px;
  margin: 36px 0 0;
  padding-top: 24px;
  border-top: 1px solid var(--about-line);
}

.page-about .about-fact dt {
  font-family: var(--sans);
  font-size: 13px;
  letter-spacing: 0.04em;
  color: var(--mute);
  margin-bottom: 8px;
}

.page-about .about-fact dd {
  margin: 0;
  font-family: var(--mono);
  font-size: 24px;
  font-weight: 600;
  color: var(--white);
  letter-spacing: -0.01em;
}

.page-about .about-fact dd .num {
  color: var(--cyan);
}

.page-about .about-hero__fig {
  margin: 40px 0 0;
}

/* ---------- 章节骨架 ---------- */
.page-about .about-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 32px;
  margin-top: 48px;
}

/* 章节索引：移动端横向滚动 */
.page-about .chapter-index {
  border-top: 1px solid var(--about-line);
  padding-top: 14px;
}

.page-about .chapter-index__title {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--mute);
  margin: 0 0 12px;
}

.page-about .chapter-index__list {
  display: flex;
  gap: 8px;
  list-style: none;
  margin: 0;
  padding: 0 0 6px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: thin;
}

.page-about .chapter-index__link {
  display: inline-flex;
  align-items: baseline;
  gap: 8px;
  white-space: nowrap;
  padding: 9px 14px;
  font-family: var(--sans);
  font-size: 14px;
  color: var(--paper);
  text-decoration: none;
  background: rgba(30, 58, 49, 0.42);
  border-left: 2px solid transparent;
  transition: border-color 0.2s ease, color 0.2s ease, background 0.2s ease;
}

.page-about .chapter-index__link:hover,
.page-about .chapter-index__link:focus-visible {
  color: var(--white);
  border-left-color: var(--cyan);
  background: rgba(30, 58, 49, 0.7);
}

.page-about .chapter-index__num {
  font-family: var(--mono);
  font-size: 12px;
  font-weight: 600;
  color: var(--cyan);
}

/* ---------- 章节内容 ---------- */
.page-about .chapter {
  padding-bottom: 52px;
  margin-bottom: 52px;
  border-bottom: 1px solid var(--about-line-soft);
  scroll-margin-top: calc(var(--bar-h) + 20px);
}

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

.page-about .chapter__num {
  font-family: var(--mono);
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.1em;
  color: var(--cyan);
  margin: 0 0 14px;
}

.page-about .chapter__title {
  font-family: var(--sans);
  font-weight: 800;
  font-size: clamp(26px, 4.6vw, 44px);
  line-height: 1.2;
  letter-spacing: -0.035em;
  color: var(--white);
  margin: 0 0 22px;
  max-width: 16em;
}

.page-about .chapter__quote {
  font-family: var(--serif);
  font-size: 18px;
  line-height: 1.75;
  color: var(--cream);
  background: rgba(201, 191, 163, 0.09);
  border-left: 3px solid var(--gold);
  padding: 16px 20px;
  margin: 0 0 28px;
  max-width: 30em;
}

.page-about .chapter__body p {
  font-family: var(--serif);
  font-size: 17px;
  line-height: 1.9;
  color: var(--paper);
  margin: 0 0 20px;
  max-width: 37em;
}

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

.page-about .inline-link {
  font-family: var(--serif);
  font-size: 16px;
  line-height: 1.85;
  color: var(--mute);
  margin: 28px 0 0;
  padding-left: 16px;
  border-left: 2px solid var(--about-line);
  max-width: 34em;
}

.page-about .inline-link a {
  color: var(--cyan);
  text-decoration: none;
  border-bottom: 1px solid rgba(53, 224, 208, 0.45);
}

.page-about .inline-link a:hover,
.page-about .inline-link a:focus-visible {
  color: var(--white);
  border-bottom-color: var(--gold);
}

/* ---------- 分段切换 ---------- */
.page-about .tabs {
  margin-top: 34px;
}

.page-about .tabs__list {
  display: flex;
  flex-wrap: wrap;
  gap: 0;
  border-bottom: 1px solid var(--about-line);
  margin-bottom: 28px;
}

.page-about .tab-btn {
  font-family: var(--sans);
  font-size: 14px;
  letter-spacing: 0.02em;
  padding: 13px 20px;
  background: transparent;
  border: 0;
  border-bottom: 2px solid transparent;
  color: var(--mute);
  cursor: pointer;
  transition: color 0.2s ease, border-color 0.2s ease;
}

.page-about .tab-btn:hover {
  color: var(--paper);
}

.page-about .tab-btn[aria-selected="true"] {
  color: var(--white);
  border-bottom-color: var(--cyan);
}

/* ---------- 竖向时间线 ---------- */
.page-about .timeline {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about .timeline__item {
  position: relative;
  padding-left: 28px;
  padding-bottom: 26px;
}

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

.page-about .timeline__item::before {
  content: "";
  position: absolute;
  left: 0;
  top: 7px;
  width: 10px;
  height: 10px;
  background: var(--ink);
  border: 2px solid var(--cyan);
  transform: rotate(45deg);
}

.page-about .timeline__item::after {
  content: "";
  position: absolute;
  left: 5px;
  top: 26px;
  bottom: 0;
  width: 1px;
  background: linear-gradient(to bottom, var(--about-line), var(--about-line-soft));
}

.page-about .timeline__item:last-child::after {
  display: none;
}

.page-about .timeline__title {
  font-family: var(--sans);
  font-weight: 700;
  font-size: 17px;
  letter-spacing: -0.01em;
  color: var(--white);
  margin: 0 0 8px;
}

.page-about .timeline__item p {
  font-family: var(--serif);
  font-size: 16px;
  line-height: 1.85;
  color: var(--paper);
  margin: 0;
  max-width: 34em;
}

/* ---------- 步骤面板 ---------- */
.page-about .step-list {
  margin-top: 26px;
  display: grid;
  gap: 12px;
}

.page-about .step {
  position: relative;
  background: rgba(30, 58, 49, 0.48);
  padding: 18px 20px 18px 24px;
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 14px), calc(100% - 14px) 100%, 0 100%);
}

.page-about .step::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--cyan);
}

.page-about .step > summary {
  list-style: none;
  cursor: pointer;
  display: flex;
  align-items: baseline;
  gap: 14px;
  outline-offset: 4px;
}

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

.page-about .step__num {
  font-family: var(--mono);
  font-size: 15px;
  font-weight: 600;
  color: var(--gold);
  letter-spacing: 0.06em;
}

.page-about .step__title {
  font-family: var(--sans);
  font-weight: 700;
  font-size: 18px;
  letter-spacing: -0.015em;
  color: var(--white);
}

.page-about .step[open] .step__title {
  color: var(--white);
}

.page-about .step__body {
  padding: 14px 0 0 38px;
}

.page-about .step__body p {
  font-family: var(--serif);
  font-size: 16px;
  line-height: 1.88;
  color: var(--paper);
  margin: 0;
  max-width: 34em;
}

/* ---------- 授权档位 ---------- */
.page-about .license-list {
  list-style: none;
  margin: 28px 0 0;
  padding: 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 14px;
}

.page-about .license {
  background: rgba(30, 58, 49, 0.42);
  border-top: 2px solid var(--gold);
  padding: 20px 18px 22px;
}

.page-about .license__num {
  font-family: var(--mono);
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.12em;
  color: var(--gold);
  margin: 0 0 12px;
}

.page-about .license__title {
  font-family: var(--sans);
  font-weight: 700;
  font-size: 19px;
  letter-spacing: -0.02em;
  color: var(--white);
  margin: 0 0 10px;
}

.page-about .license__text {
  font-family: var(--serif);
  font-size: 16px;
  line-height: 1.85;
  color: var(--paper);
  margin: 0;
}

.page-about .about-access__fig {
  margin: 34px 0 0;
}

/* ---------- 伤停补时 ---------- */
.page-about .chapter--stoppage {
  border-bottom: 0;
}

.page-about .stoppage {
  position: relative;
  padding: 28px 22px 30px;
  background: linear-gradient(140deg, rgba(255, 59, 78, 0.13), rgba(11, 31, 26, 0) 68%);
  border: 1px solid rgba(255, 59, 78, 0.34);
  clip-path: polygon(0 0, 100% 0, 100% calc(100% - 20px), calc(100% - 20px) 100%, 0 100%);
}

.page-about .stoppage__tag {
  font-family: var(--mono);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.24em;
  color: var(--pulse);
  margin: 0 0 16px;
  animation: about-pulse 2.4s ease-in-out infinite;
}

.page-about .stoppage__title {
  font-family: var(--sans);
  font-weight: 800;
  font-size: clamp(24px, 4vw, 38px);
  line-height: 1.22;
  letter-spacing: -0.032em;
  color: var(--white);
  margin: 0 0 18px;
}

.page-about .stoppage__text {
  font-family: var(--serif);
  font-size: 17px;
  line-height: 1.9;
  color: var(--paper);
  margin: 0 0 24px;
  max-width: 36em;
}

.page-about .stoppage__links {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin: 0;
}

@keyframes about-pulse {
  0%, 100% { opacity: 0.5; }
  50% { opacity: 1; }
}

/* ---------- 平板 ---------- */
@media (min-width: 640px) {
  .page-about .about-hero__facts {
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 18px;
  }

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

  .page-about .stoppage {
    padding: 36px 32px 38px;
  }
}

/* ---------- 桌面：左侧常驻章节索引 ---------- */
@media (min-width: 960px) {
  .page-about {
    padding-bottom: 112px;
  }

  .page-about .about-hero {
    padding-top: 52px;
    margin-top: 24px;
  }

  .page-about .about-hero__lede {
    font-size: 18px;
  }

  .page-about .about-hero__fig {
    margin-top: 52px;
  }

  .page-about .about-layout {
    grid-template-columns: var(--about-rail) minmax(0, 1fr);
    gap: var(--about-gutter);
    margin-top: 72px;
  }

  .page-about .chapter-index {
    position: sticky;
    top: calc(var(--bar-h) + 28px);
    align-self: start;
    padding-top: 18px;
  }

  .page-about .chapter-index__list {
    flex-direction: column;
    gap: 2px;
    overflow: visible;
    padding-bottom: 0;
  }

  .page-about .chapter-index__link {
    white-space: normal;
    background: transparent;
    padding: 10px 0 10px 14px;
    font-size: 14px;
    color: var(--mute);
  }

  .page-about .chapter-index__link:hover,
  .page-about .chapter-index__link:focus-visible {
    background: transparent;
    color: var(--white);
    border-left-color: var(--cyan);
  }

  .page-about .chapter {
    padding-bottom: 72px;
    margin-bottom: 72px;
  }

  .page-about .chapter__quote {
    font-size: 19px;
    padding: 20px 26px;
    margin-bottom: 32px;
  }

  .page-about .chapter__body p {
    font-size: 17.5px;
  }

  .page-about .license-list {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 18px;
  }

  .page-about .step__body {
    padding-left: 42px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .stoppage__tag {
    animation: none;
    opacity: 1;
  }

  .page-about .chapter-index__link {
    transition: none;
  }
}
<<<END>>>