.page-about {
  --about-rule: 1px solid var(--ink-line);
  --about-idx-w: 224px;
  --about-radius: 6px;
}

/* ---------- 面包屑 ---------- */
.page-about .about-crumb {
  padding-top: clamp(24px, 3vw, 44px);
}

/* ---------- 首屏 ---------- */
.page-about .about-hero {
  padding-top: clamp(32px, 4.5vw, 68px);
}

.page-about .about-hero__title {
  margin: 18px 0 0;
  font-size: clamp(30px, 7.4vw, 108px);
  font-weight: 200;
  line-height: 1.02;
  letter-spacing: -0.03em;
  color: var(--paper);
  max-width: 20ch;
}

.page-about .about-hero__line {
  display: block;
}

.page-about .about-hero__line--accent {
  color: var(--rosso-600);
  font-weight: 300;
}

.page-about .about-hero__lead {
  margin: clamp(22px, 2.6vw, 36px) 0 0;
  max-width: 720px;
  font-size: var(--fs-18);
  line-height: 1.78;
  color: var(--paper-72);
}

.page-about .about-hero__facts {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: clamp(32px, 4vw, 56px) 0 0;
  background: var(--ink-line);
  border: var(--about-rule);
}

.page-about .about-hero__facts > div {
  background: var(--ink-900);
  padding: 16px 18px 18px;
}

.page-about .about-hero__facts dt {
  font-size: 11px;
  letter-spacing: 0.18em;
  color: var(--slate);
  margin: 0;
}

.page-about .about-hero__facts dd {
  margin: 10px 0 0;
  font-size: clamp(22px, 3.4vw, 40px);
  line-height: 1;
  color: var(--paper);
  letter-spacing: 0.01em;
}

/* ---------- 主布局 ---------- */
.page-about .about-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: clamp(36px, 5vw, 68px);
  margin-top: clamp(52px, 7vw, 108px);
}

/* ---------- 左侧章节索引 ---------- */
.page-about .about-index__title {
  position: relative;
  margin: 0 0 14px;
  padding-left: 14px;
  font-size: 11px;
  letter-spacing: 0.18em;
  color: var(--slate);
}

.page-about .about-index__title::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.42em;
  width: 6px;
  height: 6px;
  background: var(--rosso-600);
}

.page-about .about-index__list {
  display: flex;
  gap: 0;
  margin: 0;
  padding: 0;
  list-style: none;
  overflow-x: auto;
  border-top: var(--about-rule);
  border-bottom: var(--about-rule);
  scrollbar-width: thin;
}

.page-about .about-index__item {
  flex: 0 0 auto;
  border-right: var(--about-rule);
}

.page-about .about-index__item:last-child {
  border-right: 0;
}

.page-about .about-index__link {
  display: block;
  min-width: 150px;
  padding: 12px 16px 14px;
  text-decoration: none;
  color: var(--slate);
}

.page-about .about-index__num {
  margin-right: 8px;
  font-size: 11px;
  color: var(--rosso-600);
}

.page-about .about-index__label {
  font-size: var(--fs-14);
  color: var(--paper-72);
  transition: color 0.2s var(--ease);
}

.page-about .about-index__year {
  display: block;
  margin-top: 5px;
  font-size: 11px;
  color: var(--slate);
  opacity: 0.8;
  transition: color 0.2s var(--ease);
}

.page-about .about-index__link.is-active .about-index__label {
  color: var(--paper);
}

.page-about .about-index__link.is-active .about-index__year {
  color: var(--rosso-600);
  opacity: 1;
}

/* ---------- 章节流 ---------- */
.page-about .about-flow > * + * {
  margin-top: clamp(44px, 6vw, 88px);
}

.page-about .about-sec {
  position: relative;
  padding-top: clamp(32px, 4.2vw, 60px);
  border-top: var(--about-rule);
}

.page-about .about-sec__water {
  position: absolute;
  top: clamp(24px, 3vw, 44px);
  right: 0;
  font-family: var(--font-mono);
  font-size: clamp(80px, 12vw, 168px);
  font-weight: 200;
  line-height: 0.8;
  letter-spacing: -0.04em;
  color: var(--paper);
  opacity: 0.05;
  pointer-events: none;
  user-select: none;
}

.page-about .about-sec__title {
  margin: 14px 0 0;
  max-width: 20ch;
  font-size: clamp(26px, 3.4vw, 44px);
  font-weight: 400;
  line-height: 1.22;
  letter-spacing: -0.01em;
  color: var(--paper);
}

.page-about .about-sec__tail {
  margin-top: clamp(20px, 2.4vw, 32px);
}

/* ---------- 分栏 ---------- */
.page-about .about-split {
  display: grid;
  gap: clamp(24px, 3vw, 40px);
  margin-top: clamp(26px, 3.2vw, 44px);
}

.page-about .about-split--chrono {
  margin-top: clamp(32px, 4vw, 56px);
}

.page-about .about-sec__media {
  margin: 0;
}

/* ---------- 长文 ---------- */
.page-about .prose {
  max-width: 720px;
  color: var(--paper-72);
  line-height: 1.8;
}

.page-about .prose p {
  margin: 0;
  font-size: var(--fs-18);
}

.page-about .prose p + p {
  margin-top: 1em;
}

.page-about .prose a {
  color: var(--paper);
  text-decoration: none;
  border-bottom: 1px solid var(--rosso-600);
  padding-bottom: 1px;
  transition: color 0.2s var(--ease), border-color 0.2s var(--ease);
}

.page-about .prose a:hover {
  color: var(--rosso-400);
  border-bottom-color: var(--rosso-400);
}

/* ---------- 数据来源对照 ---------- */
.page-about .source-grid {
  display: grid;
  gap: 1px;
  margin-top: clamp(26px, 3.2vw, 40px);
  background: var(--ink-line);
  border: var(--about-rule);
}

.page-about .source-grid__col {
  background: var(--ink-700);
  padding: clamp(20px, 2.6vw, 34px);
}

.page-about .source-grid__name {
  margin: 0;
  font-size: 11px;
  letter-spacing: 0.18em;
  color: var(--orange);
  font-family: var(--font-mono);
}

.page-about .source-grid__head {
  margin: 10px 0 18px;
  font-size: var(--fs-24);
  font-weight: 500;
  color: var(--paper);
}

.page-about .source-grid__list {
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: var(--about-rule);
}

.page-about .source-grid__list li {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
  padding: 10px 0;
  border-bottom: var(--about-rule);
  font-size: var(--fs-14);
  color: var(--paper-72);
}

.page-about .source-grid__list li .mono {
  font-size: 12px;
  color: var(--slate);
  white-space: nowrap;
}

/* ---------- 编年图 ---------- */
.page-about .chrono {
  margin-top: clamp(26px, 3.2vw, 44px);
  padding: clamp(18px, 2.4vw, 32px);
  border: var(--about-rule);
  background: var(--ink-700);
  box-shadow: var(--shadow-plate);
}

.page-about .chrono__svg {
  display: block;
  width: 100%;
  height: auto;
  overflow: visible;
}

.page-about .chrono__bar {
  fill: var(--ink-line);
  transition: fill 0.2s var(--ease);
}

.page-about .chrono__bar--euro {
  fill: var(--rosso-600);
}

.page-about .chrono__bar:hover {
  fill: var(--orange);
}

.page-about .chrono__axis {
  stroke: var(--ink-line);
  stroke-width: 1;
}

.page-about .chrono__mark {
  fill: var(--orange);
}

.page-about .chrono__tick {
  fill: var(--slate);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.04em;
}

.page-about .chrono__legend {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 26px;
  margin: 22px 0 0;
  padding: 0;
  list-style: none;
  font-size: 12px;
  letter-spacing: 0.06em;
  color: var(--slate);
}

.page-about .chrono__legend li {
  display: flex;
  align-items: center;
  gap: 8px;
}

.page-about .chrono__legend .sw {
  width: 10px;
  height: 10px;
  display: inline-block;
}

.page-about .chrono__legend .sw--euro {
  background: var(--rosso-600);
}

.page-about .chrono__legend .sw--league {
  background: var(--ink-line);
}

.page-about .chrono__legend .sw--mark {
  background: var(--orange);
}

/* ---------- 使用场景 ---------- */
.page-about .usecase-list {
  margin: clamp(26px, 3.2vw, 44px) 0 0;
  padding: 0;
  list-style: none;
  border-top: var(--about-rule);
}

.page-about .usecase {
  display: grid;
  grid-template-columns: 38px minmax(0, 1fr);
  gap: clamp(12px, 2vw, 26px);
  padding: clamp(18px, 2.2vw, 28px) 0;
  border-bottom: var(--about-rule);
}

.page-about .usecase__num {
  font-size: var(--fs-14);
  color: var(--rosso-600);
  padding-top: 0.3em;
}

.page-about .usecase__title {
  margin: 0 0 8px;
  font-size: var(--fs-18);
  font-weight: 500;
  color: var(--paper);
}

.page-about .usecase__text {
  margin: 0;
  max-width: 640px;
  font-size: var(--fs-14);
  line-height: 1.8;
  color: var(--paper-72);
}

/* ---------- 联系方式 ---------- */
.page-about .channel-list {
  display: grid;
  gap: 1px;
  margin: clamp(26px, 3.2vw, 44px) 0 0;
  padding: 0;
  list-style: none;
  background: var(--ink-line);
  border: var(--about-rule);
}

.page-about .channel {
  background: var(--ink-900);
  padding: clamp(20px, 2.6vw, 32px);
}

.page-about .channel__label {
  margin: 0;
  font-size: 11px;
  letter-spacing: 0.18em;
  color: var(--rosso-600);
}

.page-about .channel__value {
  margin: 12px 0 0;
  font-size: clamp(18px, 2.4vw, 28px);
  color: var(--paper);
  word-break: break-all;
}

.page-about .channel__note {
  margin: 12px 0 0;
  max-width: 560px;
  font-size: var(--fs-14);
  line-height: 1.75;
  color: var(--slate);
}

/* ---------- 页尾收束 ---------- */
.page-about .about-end {
  margin-top: clamp(52px, 7vw, 104px);
  padding: clamp(26px, 3.4vw, 44px) 0 clamp(52px, 7vw, 96px);
  border-top: var(--about-rule);
}

.page-about .about-end__num {
  display: block;
  margin-bottom: 12px;
  font-size: 12px;
  letter-spacing: 0.18em;
  color: var(--orange);
}

.page-about .about-end__note {
  margin: 0;
  max-width: 660px;
  font-size: var(--fs-18);
  line-height: 1.7;
  color: var(--paper-72);
}

/* ---------- 响应式 ---------- */
@media (max-width: 767px) {
  .page-about .about-sec__water {
    display: none;
  }
}

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

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

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

  .page-about .channel:last-child {
    grid-column: 1 / -1;
  }
}

@media (min-width: 860px) {
  .page-about .about-split {
    grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
    align-items: start;
  }

  .page-about .about-split--media-first {
    grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
  }
}

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

  .page-about .about-index {
    position: sticky;
    top: 104px;
    align-self: start;
  }

  .page-about .about-index__list {
    display: block;
    overflow: visible;
    border-bottom: 0;
  }

  .page-about .about-index__item {
    border-right: 0;
    border-bottom: var(--about-rule);
  }

  .page-about .about-index__item:last-child {
    border-bottom: 0;
  }

  .page-about .about-index__link {
    position: relative;
    min-width: 0;
    padding: 13px 0 14px 16px;
  }

  .page-about .about-index__link::before {
    content: "";
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 2px;
    background: transparent;
    transition: background 0.2s var(--ease);
  }

  .page-about .about-index__link.is-active::before {
    background: var(--rosso-600);
  }

  .page-about .about-index__link:hover .about-index__label {
    color: var(--paper);
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-index__link::before,
  .page-about .about-index__label,
  .page-about .about-index__year,
  .page-about .chrono__bar,
  .page-about .prose a {
    transition: none;
  }
}
</PAGE_CSS>