.page-about {
  position: relative;
  overflow-x: clip;
}

.page-about .about-hero {
  padding: clamp(24px, 4vw, 48px) 0 clamp(32px, 5vw, 64px);
}

.page-about .about-hero__meta {
  margin: 0 0 18px;
  font-size: 13px;
  letter-spacing: 0.12em;
  color: var(--mist);
}

.page-about .about-hero__title {
  margin: 0 0 22px;
  font-size: clamp(30px, 6vw, 74px);
  font-weight: 900;
  line-height: 1.08;
  letter-spacing: -0.01em;
  color: var(--ice);
  max-width: 18em;
}

.page-about .about-hero__em {
  color: var(--cyan);
  text-shadow: 0 0 26px rgba(34, 243, 228, 0.38);
}

.page-about .about-hero__lead {
  margin: 0 0 34px;
  max-width: 64ch;
  font-size: clamp(15px, 1.6vw, 17px);
  line-height: 1.85;
  color: var(--mist);
}

.page-about .about-stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 0;
  padding: 0;
  list-style: none;
  border: 1px solid var(--line);
  background: var(--line);
}

.page-about .about-stats > li {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 18px 16px;
  background: var(--ink-800);
}

.page-about .about-stats__n {
  font-size: clamp(22px, 3vw, 32px);
  font-weight: 700;
  line-height: 1;
  color: var(--cyan);
}

.page-about .about-stats__l {
  font-size: 13px;
  letter-spacing: 0.04em;
  color: var(--mist);
}

.page-about .about-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 26px;
  padding-bottom: clamp(48px, 8vw, 96px);
}

/* 章节目录 */
.page-about .about-index {
  border: 1px solid var(--line);
  background: linear-gradient(180deg, rgba(20, 26, 69, 0.92), rgba(10, 14, 42, 0.92));
  padding: 16px;
}

.page-about .about-index__title {
  margin: 0 0 12px;
  font-size: 12px;
  letter-spacing: 0.16em;
  color: var(--mist);
}

.page-about .about-index__list {
  display: flex;
  gap: 10px;
  margin: 0;
  padding: 0 0 4px;
  list-style: none;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
}

.page-about .about-index__list::-webkit-scrollbar {
  display: none;
}

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

.page-about .about-index__link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border: 1px solid var(--line);
  color: var(--ice);
  font-size: 13px;
  text-decoration: none;
  white-space: nowrap;
  transition: border-color 0.2s ease, color 0.2s ease, background-color 0.2s ease;
}

.page-about .about-index__link .mono {
  font-size: 12px;
  color: var(--violet);
}

.page-about .about-index__link:hover {
  border-color: var(--line-strong);
  color: var(--cyan);
}

/* 章节 */
.page-about .about-chapter {
  position: relative;
  padding: clamp(26px, 4vw, 42px) 0 clamp(30px, 5vw, 52px);
  border-top: 1px solid var(--line);
  scroll-margin-top: 152px;
}

.page-about .about-chapter::before {
  content: "";
  position: absolute;
  top: -1px;
  left: 0;
  width: 120px;
  height: 1px;
  background: linear-gradient(90deg, var(--violet), rgba(34, 243, 228, 0.3));
}

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

.page-about .about-chapter:first-child::before {
  display: none;
}

.page-about .about-chapter__head {
  display: flex;
  align-items: center;
  gap: 16px;
  margin-bottom: 20px;
}

.page-about .about-chapter__title {
  margin: 0;
  font-size: clamp(20px, 3.2vw, 30px);
  font-weight: 800;
  letter-spacing: -0.01em;
  color: var(--ice);
}

.page-about .about-num {
  position: relative;
  flex: 0 0 auto;
  display: grid;
  place-items: center;
  width: 46px;
  height: 46px;
  border-radius: 50%;
  font-size: 14px;
  color: var(--ice);
  background: radial-gradient(circle at 32% 28%, rgba(108, 76, 255, 0.5), rgba(10, 14, 42, 0.95) 72%);
  border: 1px solid rgba(108, 76, 255, 0.55);
  box-shadow: inset 0 1px 0 rgba(237, 242, 255, 0.08);
}

.page-about .about-num::after {
  content: "";
  position: absolute;
  inset: -5px;
  border-radius: 50%;
  background: conic-gradient(from 210deg, var(--violet), var(--cyan), rgba(34, 243, 228, 0) 72%);
  -webkit-mask: radial-gradient(farthest-side, rgba(0, 0, 0, 0) calc(100% - 2px), #000 calc(100% - 2px));
  mask: radial-gradient(farthest-side, rgba(0, 0, 0, 0) calc(100% - 2px), #000 calc(100% - 2px));
  opacity: 0.85;
  pointer-events: none;
}

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

.page-about .about-chapter__text p,
.page-about .about-chapter__lead {
  margin: 0 0 16px;
  font-size: 16px;
  line-height: 1.85;
  color: var(--mist);
}

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

.page-about .about-chapter__lead {
  max-width: 68ch;
}

/* 图 */
.page-about .about-figure {
  margin: 0;
  border: 1px solid var(--line);
  background: var(--ink-700);
  box-shadow: var(--shadow-card);
}

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

.page-about .about-figure--side img {
  aspect-ratio: 14 / 9;
}

.page-about .about-figure--wide img {
  aspect-ratio: 16 / 7;
}

.page-about .about-figure--tall img {
  aspect-ratio: 3 / 2;
}

.page-about .about-figure figcaption {
  padding: 10px 14px;
  border-top: 1px solid var(--line);
  font-size: 13px;
  letter-spacing: 0.03em;
  color: var(--mist);
}

.page-about .about-figure--wide {
  margin-bottom: 24px;
}

/* 时间轴 */
.page-about .about-timeline {
  margin-top: 28px;
  padding: 16px 12px 10px;
  border: 1px solid var(--line);
  background: linear-gradient(180deg, rgba(20, 26, 69, 0.75), rgba(6, 8, 24, 0.92));
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.page-about .about-tl {
  display: block;
  width: 100%;
  min-width: 660px;
  height: auto;
}

.page-about .about-tl__axis {
  stroke: rgba(152, 163, 198, 0.42);
  stroke-width: 1.5;
  stroke-dasharray: 6 6;
}

.page-about .about-tl__node circle {
  fill: var(--ink-900);
  stroke: var(--violet);
  stroke-width: 2.5;
  transition: stroke 0.2s ease;
}

.page-about .about-tl__node--hi circle {
  stroke: var(--cyan);
  filter: drop-shadow(0 0 8px rgba(34, 243, 228, 0.55));
}

.page-about .about-tl__year {
  fill: var(--amber);
  font-family: var(--font-mono);
  font-size: 19px;
  font-weight: 700;
  text-anchor: middle;
}

.page-about .about-tl__label {
  fill: var(--ice);
  font-size: 14px;
  text-anchor: middle;
}

.page-about .about-tl__tip {
  fill: var(--cyan);
  font-size: 12px;
  text-anchor: middle;
  opacity: 0;
  transition: opacity 0.2s ease;
}

.page-about .about-tl__node:hover circle {
  stroke: var(--cyan);
}

.page-about .about-tl__node:hover .about-tl__tip {
  opacity: 1;
}

/* 三条内容线 */
.page-about .about-lines {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 18px;
}

.page-about .about-line {
  position: relative;
  padding: 24px 20px 20px;
  border: 1px solid var(--line);
  background: linear-gradient(180deg, rgba(20, 26, 69, 0.86), rgba(10, 14, 42, 0.86));
  overflow: hidden;
  transition: transform 0.25s ease, box-shadow 0.25s ease, border-color 0.25s ease;
}

.page-about .about-line::after {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  width: 3px;
}

.page-about .about-line--cyan::after {
  background: var(--cyan);
}

.page-about .about-line--magenta::after {
  background: var(--magenta);
}

.page-about .about-line--violet::after {
  background: var(--violet);
}

.page-about .about-line:hover {
  transform: translateY(-4px);
  border-color: var(--line-strong);
  box-shadow: var(--shadow-card);
}

.page-about .about-line h3 {
  margin: 0 0 10px;
  font-size: 18px;
  font-weight: 800;
  color: var(--ice);
}

.page-about .about-line p {
  margin: 0 0 12px;
  font-size: 15px;
  line-height: 1.8;
  color: var(--mist);
}

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

.page-about .about-link {
  display: inline-block;
  padding-bottom: 2px;
  border-bottom: 1px solid rgba(34, 243, 228, 0.45);
  font-size: 14px;
  color: var(--cyan);
  text-decoration: none;
  transition: color 0.2s ease, border-color 0.2s ease;
}

.page-about .about-link:hover {
  color: var(--ice);
  border-bottom-color: var(--amber);
}

.page-about .about-note {
  margin: 22px 0 0;
  padding: 15px 18px;
  border-left: 3px solid var(--amber);
  background: rgba(255, 176, 32, 0.07);
  font-size: 15px;
  line-height: 1.8;
  color: var(--ice);
}

/* 四象限 */
.page-about .about-quad {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1px;
  margin-top: 22px;
  border: 1px solid var(--line);
  background: var(--line);
}

.page-about .about-quad__cell {
  position: relative;
  padding: 22px 20px;
  background: var(--ink-800);
  transition: background-color 0.25s ease;
}

.page-about .about-quad__cell:hover {
  background: var(--ink-700);
}

.page-about .about-quad__k {
  display: inline-block;
  margin-bottom: 12px;
  padding: 2px 9px;
  border: 1px solid rgba(108, 76, 255, 0.55);
  font-size: 12px;
  letter-spacing: 0.12em;
  color: var(--violet);
}

.page-about .about-quad__cell h3 {
  margin: 0 0 8px;
  font-size: 17px;
  font-weight: 800;
  color: var(--ice);
}

.page-about .about-quad__cell p {
  margin: 0;
  font-size: 15px;
  line-height: 1.8;
  color: var(--mist);
}

/* 继续深入 */
.page-about .about-next {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 16px;
  margin-top: 24px;
}

.page-about .about-next__card {
  display: block;
  padding: 24px 20px;
  border: 1px solid var(--line);
  background: linear-gradient(160deg, rgba(20, 26, 69, 0.95), rgba(6, 8, 24, 0.95));
  color: inherit;
  text-decoration: none;
  transition: transform 0.25s ease, border-color 0.25s ease, box-shadow 0.25s ease;
}

.page-about .about-next__card:hover {
  transform: translateY(-4px);
  border-color: rgba(34, 243, 228, 0.6);
  box-shadow: var(--glow-cyan);
}

.page-about .about-next__k {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--magenta);
}

.page-about .about-next__card h3 {
  margin: 10px 0 8px;
  font-size: 18px;
  font-weight: 800;
  color: var(--ice);
}

.page-about .about-next__card p {
  margin: 0;
  font-size: 14px;
  line-height: 1.75;
  color: var(--mist);
}

/* 返回顶部 */
.page-about .about-top {
  position: fixed;
  right: 18px;
  bottom: 22px;
  z-index: 30;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 11px 18px;
  border: 0;
  border-radius: 999px;
  font-family: inherit;
  font-size: 13px;
  color: var(--ink-900);
  background: var(--cyan);
  box-shadow: var(--glow-cyan);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: opacity 0.25s ease, transform 0.25s ease, visibility 0.25s ease;
}

.page-about .about-top.is-on,
.page-about .about-top.is-in {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

/* 平板及以上 */
@media (min-width: 760px) {
  .page-about .about-stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

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

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

@media (min-width: 900px) {
  .page-about .about-lines {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .page-about .about-chapter__grid {
    grid-template-columns: minmax(0, 1.4fr) minmax(0, 1fr);
    gap: 36px;
    align-items: start;
  }

  .page-about .about-chapter__grid--media-first {
    grid-template-columns: minmax(0, 1fr) minmax(0, 1.4fr);
  }

  .page-about .about-chapter__grid--media-first .about-figure {
    order: 1;
  }

  .page-about .about-chapter__grid--media-first .about-chapter__text {
    order: 2;
  }
}

/* 桌面：左侧固定章节目录 */
@media (min-width: 1080px) {
  .page-about .about-layout {
    grid-template-columns: 236px minmax(0, 1fr);
    gap: 60px;
  }

  .page-about .about-index {
    position: sticky;
    top: 144px;
    align-self: start;
    padding: 18px 14px;
  }

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

  .page-about .about-index__list > li {
    flex: 1 1 auto;
  }

  .page-about .about-index__link {
    justify-content: flex-start;
    width: 100%;
    padding: 9px 10px;
    border: 0;
    border-left: 2px solid transparent;
    white-space: normal;
    line-height: 1.5;
  }

  .page-about .about-index__link:hover {
    border-left-color: var(--amber);
    color: var(--ice);
    background: rgba(255, 176, 32, 0.06);
  }

  .page-about .about-index__link[aria-current="true"],
  .page-about .about-index__link.is-on {
    border-left-color: var(--cyan);
    color: var(--cyan);
    background: rgba(34, 243, 228, 0.07);
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .about-line,
  .page-about .about-next__card,
  .page-about .about-top,
  .page-about .about-tl__tip {
    transition: none;
  }

  .page-about .about-line:hover,
  .page-about .about-next__card:hover {
    transform: none;
  }
}