.page-about {
  --about-measure: 44rem;
  --about-wide: 68rem;
  --about-stage-num: clamp(1.75rem, 6vw, 3rem);
}

.page-about .about-col {
  max-width: var(--about-measure);
}

.page-about .about-wide {
  max-width: var(--about-wide);
}

/* 首屏 */
.page-about .about-hero {
  position: relative;
  padding-top: 1.25rem;
}

.page-about .about-hero h1 {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(2rem, 8vw, 3.9rem);
  line-height: 1.08;
  letter-spacing: -0.02em;
  margin: 0.6rem 0 1.15rem;
  max-width: 22ch;
}

.page-about .about-hero .lede {
  color: var(--text);
}

.page-about .about-hero::after {
  content: "";
  display: block;
  width: min(100%, 22rem);
  height: 2px;
  margin-top: 2.5rem;
  background: linear-gradient(90deg, var(--cyan), var(--violet) 55%, transparent);
}

.page-about .about-stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 2.5rem 0 0;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .about-stat {
  background: var(--ink-2);
  padding: 1rem 1.1rem 1.15rem;
}

.page-about .about-stat dt {
  margin: 0;
  font-size: 0.8rem;
  letter-spacing: 0.04em;
  color: var(--muted);
}

.page-about .about-stat dd {
  margin: 0.4rem 0 0;
  font-family: var(--font-body);
  font-size: 1.15rem;
  color: var(--text);
}

.page-about .about-stat dd .mono {
  color: var(--amber);
  font-size: 1.45rem;
  letter-spacing: -0.02em;
}

/* 章节索引 */
.page-about .about-index {
  margin-top: 3rem;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  background: var(--ink-3);
}

.page-about .about-index__list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem 1.6rem;
  list-style: none;
  margin: 0;
  padding: 0.85rem 0;
}

.page-about .about-index__list a {
  display: inline-flex;
  align-items: baseline;
  gap: 0.45rem;
  padding-bottom: 2px;
  font-size: 0.95rem;
  color: var(--muted);
  border-bottom: 1px solid transparent;
  transition: color 0.18s var(--ease), border-color 0.18s var(--ease);
}

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

.page-about .about-index__list .mono {
  font-size: 0.78rem;
  color: var(--blue);
}

/* 章节标题 */
.page-about .sec-head {
  max-width: var(--about-measure);
  margin-bottom: 1.75rem;
}

.page-about .sec-head h2 {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(1.55rem, 5vw, 2.5rem);
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin: 0.5rem 0 0;
}

.page-about .sec-head p {
  margin: 0.85rem 0 0;
  color: var(--muted);
}

/* 时间线 */
.page-about .tl {
  list-style: none;
  margin: 2.25rem 0 0;
  padding: 0;
  counter-reset: stage;
}

.page-about .tl__item {
  position: relative;
  padding-left: 1.1rem;
  padding-bottom: 1.9rem;
  border-left: 1px solid var(--line);
}

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

.page-about .tl__item::before {
  content: "";
  position: absolute;
  left: -4px;
  top: 1.05rem;
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--cyan);
  box-shadow: 0 0 0 3px rgba(53, 242, 214, 0.14);
}

.page-about .tl__node {
  border: 0;
}

.page-about .tl__summary {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.6rem 1rem;
  padding: 0.3rem 0;
  cursor: pointer;
  list-style: none;
}

.page-about .tl__summary::-webkit-details-marker {
  display: none;
}

.page-about .tl__summary::before {
  counter-increment: stage;
  content: counter(stage, decimal-leading-zero);
  font-family: var(--font-mono);
  font-size: var(--about-stage-num);
  line-height: 1;
  letter-spacing: -0.03em;
  color: var(--violet-soft);
}

.page-about .tl__summary::after {
  content: "+";
  margin-left: auto;
  align-self: center;
  font-family: var(--font-mono);
  font-size: 1.15rem;
  color: var(--muted-2);
}

.page-about .tl__node[open] .tl__summary::after {
  content: "–";
  color: var(--cyan);
}

.page-about .tl__title {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(1.2rem, 4vw, 1.7rem);
  letter-spacing: -0.01em;
  color: var(--text);
}

.page-about .tl__year {
  align-self: center;
}

.page-about .tl__body {
  max-width: var(--about-measure);
  padding: 0.4rem 0 0.9rem;
}

.page-about .tl__body p {
  color: var(--muted);
}

.page-about .tl__scene {
  margin-top: 0.9rem;
  padding-left: 0.9rem;
  border-left: 2px solid var(--violet);
  color: var(--text);
  font-size: 0.95rem;
}

/* 团队 */
.page-about .about-media {
  margin: 0 0 2.25rem;
}

.page-about .team-grid {
  display: block;
}

.page-about .roles {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
}

.page-about .role {
  position: relative;
  padding: 1.25rem 1.25rem 1.25rem 1.4rem;
  background: var(--ink-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  transition: border-color 0.22s var(--ease), transform 0.22s var(--ease);
}

.page-about .role::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0;
  width: 2px;
  height: 100%;
  background: linear-gradient(180deg, var(--violet), transparent);
  opacity: 0.75;
}

.page-about .role:hover,
.page-about .role:focus-within {
  border-color: var(--violet);
  transform: translateY(-2px);
}

.page-about .role__name {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.25rem;
  letter-spacing: -0.01em;
  margin: 0;
}

.page-about .role__lead {
  margin: 0.6rem 0 0;
  color: var(--muted);
  font-size: 0.97rem;
}

.page-about .role__detail {
  margin: 0;
  max-height: 0;
  overflow: hidden;
  opacity: 0;
  font-size: 0.9rem;
  line-height: 1.7;
  color: var(--muted-2);
  transition: max-height 0.28s var(--ease), opacity 0.22s var(--ease), margin 0.22s var(--ease);
}

.page-about .role:hover .role__detail,
.page-about .role:focus-within .role__detail {
  max-height: 16rem;
  opacity: 1;
  margin-top: 0.7rem;
}

/* 数据旅程 */
.page-about .journey {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
}

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

.page-about .steps__item {
  position: relative;
  padding: 0 0 1.6rem 3.1rem;
}

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

.page-about .steps__num {
  position: absolute;
  left: 0;
  top: 0.1rem;
  font-size: 1.05rem;
  color: var(--blue);
}

.page-about .steps__title {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.15rem;
  margin: 0 0 0.5rem;
}

.page-about .steps__item p {
  margin: 0;
  color: var(--muted);
}

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

/* 覆盖与节奏 */
.page-about .pulse {
  border-top: 1px solid var(--line);
}

.page-about .pulse__row {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.5rem;
  padding: 1.4rem 0;
  border-bottom: 1px solid var(--line);
}

.page-about .pulse__num {
  font-size: clamp(2.4rem, 11vw, 4.2rem);
  line-height: 0.95;
  letter-spacing: -0.04em;
  color: var(--amber);
}

.page-about .pulse__text {
  margin: 0;
  color: var(--muted);
}

.page-about .pulse__note {
  max-width: var(--about-measure);
  margin: 1.6rem 0 0;
  color: var(--muted);
}

/* 合作与白皮书 */
.page-about .partners {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
}

.page-about .partners__text p {
  color: var(--muted);
}

.page-about .quote {
  margin: 1.6rem 0;
  padding: 1.15rem 1.25rem;
  background: var(--ink-3);
  border: 1px solid var(--line);
  border-left: 3px solid var(--cyan);
}

.page-about .quote p {
  margin: 0;
  color: var(--text);
  font-size: 0.97rem;
}

.page-about .partners__text .btn {
  margin-top: 0.5rem;
}

.page-about .partners__media {
  margin: 0;
  max-width: 26rem;
}

/* 下一阶段 */
.page-about .next-title {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(1.5rem, 5vw, 2.3rem);
  line-height: 1.18;
  letter-spacing: -0.02em;
  margin: 0.5rem 0 0;
}

.page-about .about-cta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-top: 1.75rem;
}

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

  .page-about .pulse__row {
    grid-template-columns: 9.5rem minmax(0, 1fr);
    align-items: baseline;
    gap: 1.5rem;
  }
}

@media (min-width: 720px) {
  .page-about .roles {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

@media (min-width: 900px) {
  .page-about .tl__item {
    padding-left: 2rem;
    padding-bottom: 2.25rem;
  }

  .page-about .journey {
    grid-template-columns: minmax(0, 1.1fr) minmax(0, 0.9fr);
    align-items: start;
    gap: 3rem;
  }

  .page-about .journey__media {
    margin-top: 4.5rem;
  }

  .page-about .partners {
    grid-template-columns: minmax(0, 1.25fr) minmax(0, 0.75fr);
    align-items: start;
    gap: 3.5rem;
  }

  .page-about .partners__media {
    max-width: none;
    margin-top: 1.5rem;
  }
}

@media (max-width: 719px) {
  .page-about .role__detail {
    max-height: none;
    opacity: 1;
    margin-top: 0.7rem;
  }

  .page-about .role:hover,
  .page-about .role:focus-within {
    transform: none;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about * {
    transition: none !important;
  }
}