.page-about {
  --about-gap: clamp(24px, 3.4vw, 52px);
  --about-chapter-gap: clamp(64px, 9vw, 132px);
  --about-radius: 4px;
  background: var(--ink-800);
  color: var(--white);
  overflow-x: clip;
}

.page-about .breadcrumb {
  padding-top: calc(var(--head-h) + 18px);
  font-size: 12px;
  letter-spacing: .1em;
}

.page-about .breadcrumb ol {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 0;
  padding: 0;
  list-style: none;
  color: var(--mist);
}

.page-about .breadcrumb li + li::before {
  content: "/";
  margin-right: 8px;
  color: var(--ink-600);
}

.page-about .breadcrumb a {
  color: var(--mist);
  text-decoration: none;
  transition: color .24s var(--ease);
}

.page-about .breadcrumb a:hover,
.page-about .breadcrumb a:focus-visible {
  color: var(--flame);
}

/* ---------- 首屏 ---------- */

.page-about .about-hero {
  position: relative;
  padding: clamp(28px, 5vw, 64px) 0 clamp(40px, 6vw, 80px);
  isolation: isolate;
}

.page-about .about-hero::before {
  content: "";
  position: absolute;
  z-index: -1;
  top: 4%;
  right: -14%;
  width: min(72%, 640px);
  aspect-ratio: 1 / 1;
  background:
    linear-gradient(142deg, rgba(30, 86, 67, .58) 0%, rgba(255, 92, 26, .18) 58%, rgba(46, 125, 255, .12) 100%);
  border: 1px solid var(--line);
  clip-path: polygon(42% 0, 100% 0, 100% 100%, 0 100%);
  pointer-events: none;
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  z-index: -1;
  left: 0;
  bottom: 6%;
  width: min(30%, 240px);
  height: 3px;
  background: linear-gradient(90deg, var(--flame) 0%, var(--sand) 55%, var(--blue) 100%);
  pointer-events: none;
}

.page-about .about-hero__inner {
  position: relative;
}

.page-about .about-hero__title {
  margin: 16px 0 0;
  font-size: clamp(34px, 7.4vw, 82px);
  line-height: 1.05;
  font-weight: 400;
  letter-spacing: .008em;
  max-width: 16ch;
}

.page-about .about-hero__accent {
  color: var(--flame);
}

.page-about .about-hero__lede {
  margin: clamp(20px, 3vw, 32px) 0 0;
  max-width: 34em;
  font-size: 17px;
  line-height: 1.85;
  color: rgba(244, 247, 245, .86);
}

.page-about .about-facts {
  list-style: none;
  margin: clamp(30px, 4.4vw, 52px) 0 0;
  padding: clamp(20px, 2.6vw, 28px) 0 0;
  border-top: 1px solid var(--line);
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px 14px;
}

.page-about .about-facts__item {
  display: flex;
  flex-direction: column;
  gap: 6px;
  min-width: 0;
}

.page-about .about-facts__label {
  font-size: 12px;
  letter-spacing: .14em;
  color: var(--mist);
  line-height: 1.6;
}

/* ---------- 索引 + 内容流 ---------- */

.page-about .about-layout {
  padding-bottom: clamp(56px, 8vw, 120px);
}

.page-about .about-index {
  padding-bottom: 26px;
  border-bottom: 1px solid var(--line);
  margin-bottom: clamp(34px, 5vw, 56px);
}

.page-about .about-index__title {
  margin: 0 0 12px;
  font-size: 12px;
  letter-spacing: .18em;
  color: var(--mist);
}

.page-about .about-index__list {
  list-style: none;
  margin: 0;
  padding: 0 0 4px;
  display: flex;
  gap: 18px;
  overflow-x: auto;
  scrollbar-width: none;
  -webkit-overflow-scrolling: touch;
}

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

.page-about .about-index__link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  white-space: nowrap;
  font-size: 13px;
  letter-spacing: .04em;
  color: var(--mist);
  text-decoration: none;
  padding-bottom: 2px;
  border-bottom: 1px solid transparent;
  transition: color .24s var(--ease), border-color .24s var(--ease);
}

.page-about .about-index__link:hover,
.page-about .about-index__link:focus-visible {
  color: var(--flame);
  border-bottom-color: var(--flame);
}

.page-about .about-index__no {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 12px;
  color: var(--flame);
}

/* ---------- 章节 ---------- */

.page-about .about-chapter + .about-chapter {
  margin-top: var(--about-chapter-gap);
}

.page-about .about-chapter__head {
  display: flex;
  align-items: flex-start;
  gap: clamp(12px, 2.2vw, 26px);
  margin-bottom: clamp(18px, 2.4vw, 28px);
}

.page-about .about-chapter__no {
  flex: none;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: clamp(42px, 8vw, 78px);
  line-height: .8;
  letter-spacing: -.02em;
  color: var(--flame);
  opacity: .9;
}

.page-about .about-chapter__head h2 {
  margin: 0;
  font-size: clamp(23px, 3.3vw, 40px);
  line-height: 1.2;
  font-weight: 400;
  letter-spacing: .008em;
  max-width: 22ch;
}

.page-about .about-chapter__body p {
  margin: 0 0 1.2em;
  max-width: 34em;
  font-size: 17px;
  line-height: 1.85;
  color: rgba(244, 247, 245, .84);
}

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

.page-about .about-chapter__stat {
  margin: clamp(22px, 3vw, 32px) 0 0;
  padding-left: 18px;
  border-left: 2px solid var(--flame);
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 6px 12px;
  font-size: 14px;
  line-height: 1.7;
  color: var(--mist);
}

.page-about .about-chapter__sep {
  color: var(--ink-600);
}

/* ---------- 团队分工 ---------- */

.page-about .about-team {
  margin-top: clamp(26px, 3.6vw, 42px);
  display: grid;
  gap: clamp(22px, 3vw, 34px);
}

.page-about .about-team__media {
  margin: 0;
  border: 1px solid var(--line);
  background: var(--ink-700);
}

.page-about .about-team__panel {
  min-width: 0;
}

.page-about .about-bars {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: clamp(20px, 2.6vw, 28px);
}

.page-about .about-bar__head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 10px;
}

.page-about .about-bar__name {
  font-size: 16px;
  letter-spacing: .05em;
  color: var(--white);
}

.page-about .about-bar__count {
  display: inline-flex;
  align-items: baseline;
  gap: 4px;
  color: var(--white);
}

.page-about .about-bar__track {
  display: block;
  height: 6px;
  border-radius: 999px;
  background: var(--ink-700);
  border: 1px solid var(--line);
  overflow: hidden;
}

.page-about .about-bar__fill {
  display: block;
  height: 100%;
  width: var(--w, 0%);
  border-radius: 999px;
  background: var(--blue);
  transition: width .9s var(--ease);
}

.page-about .about-bar--a .about-bar__fill { background: var(--blue); }
.page-about .about-bar--b .about-bar__fill { background: var(--flame); }
.page-about .about-bar--c .about-bar__fill { background: var(--sand); }

.page-about .about-bar__desc {
  margin: 12px 0 0;
  max-width: 34em;
  font-size: 14px;
  line-height: 1.8;
  color: var(--mist);
}

/* ---------- 三道流程 ---------- */

.page-about .about-checks {
  list-style: none;
  margin: clamp(26px, 3.6vw, 40px) 0 0;
  padding: 0;
  display: grid;
  gap: 16px;
}

.page-about .about-check {
  border: 1px solid var(--line);
  border-top: 2px solid var(--flame);
  border-radius: var(--about-radius);
  background: linear-gradient(160deg, var(--ink-700) 0%, rgba(11, 43, 34, .9) 100%);
  padding: clamp(20px, 2.6vw, 28px);
  min-width: 0;
}

.page-about .about-check:nth-child(1) { border-top-color: var(--blue); }
.page-about .about-check:nth-child(2) { border-top-color: var(--flame); }
.page-about .about-check:nth-child(3) { border-top-color: var(--sand); }

.page-about .about-check__step {
  margin: 0 0 12px;
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: .18em;
  color: var(--mist);
}

.page-about .about-check__title {
  margin: 0 0 10px;
  font-size: clamp(18px, 2vw, 22px);
  font-weight: 400;
  letter-spacing: .02em;
  color: var(--white);
}

.page-about .about-check__text {
  margin: 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--mist);
}

/* ---------- 协作网络 ---------- */

.page-about .about-collab {
  margin-top: clamp(26px, 3.6vw, 42px);
  display: grid;
  gap: clamp(24px, 3.4vw, 40px);
  align-items: center;
}

.page-about .about-collab__map {
  display: grid;
  gap: 20px;
}

.page-about .collab-map {
  display: block;
  width: 100%;
  max-width: 360px;
  height: auto;
  margin: 0 auto;
}

.page-about .collab-map__ring {
  fill: none;
  stroke-width: 1.4;
}

.page-about .collab-map__ring--club {
  stroke: var(--flame);
  stroke-dasharray: 5 7;
  opacity: .85;
}

.page-about .collab-map__ring--youth {
  stroke: var(--blue);
  stroke-dasharray: 4 6;
  opacity: .7;
}

.page-about .collab-map__ring--research {
  stroke: var(--sand);
  opacity: .85;
}

.page-about .collab-map__core {
  fill: var(--flame);
}

.page-about .collab-map__dot--club { fill: var(--flame); }
.page-about .collab-map__dot--youth { fill: var(--blue); }
.page-about .collab-map__dot--research { fill: var(--sand); }

.page-about .about-collab__legend {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 14px;
}

.page-about .about-collab__legend-item {
  display: flex;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 8px;
  font-size: 14px;
  line-height: 1.7;
  color: var(--mist);
}

.page-about .about-collab__swatch {
  align-self: center;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  flex: none;
}

.page-about .about-collab__swatch--club { background: var(--flame); }
.page-about .about-collab__swatch--youth { background: var(--blue); }
.page-about .about-collab__swatch--research { background: var(--sand); }

.page-about .about-collab__legend-text {
  color: var(--mist);
}

.page-about .about-collab__media {
  margin: 0;
  border: 1px solid var(--line);
  background: var(--ink-700);
}

/* ---------- 档案时间轴 ---------- */

.page-about .about-archive {
  position: relative;
  margin-top: clamp(26px, 3.6vw, 42px);
  border: 1px solid var(--line);
  border-radius: var(--about-radius);
  overflow: hidden;
  isolation: isolate;
}

.page-about .about-archive__bg {
  position: absolute;
  inset: 0;
  margin: 0;
  z-index: -1;
}

.page-about .about-archive__bg img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  opacity: .18;
}

.page-about .about-archive__bg::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg, rgba(11, 43, 34, .94) 0%, rgba(5, 19, 15, .97) 100%);
}

.page-about .about-timeline {
  list-style: none;
  margin: 0;
  padding: clamp(24px, 3.4vw, 42px);
}

.page-about .about-timeline__item {
  position: relative;
  padding: 0 0 clamp(24px, 3vw, 34px) clamp(24px, 3vw, 32px);
  border-left: 1px dashed var(--line-strong);
}

.page-about .about-timeline__item:last-child {
  padding-bottom: 0;
  border-left-color: transparent;
}

.page-about .about-timeline__node {
  position: absolute;
  left: -5px;
  top: 6px;
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--sand);
  box-shadow: 0 0 0 4px rgba(217, 178, 95, .16);
}

.page-about .about-timeline__card {
  border: 1px solid var(--line);
  border-radius: var(--about-radius);
  background: var(--glass);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  padding: clamp(16px, 2.2vw, 22px);
}

.page-about .about-timeline__phase {
  margin: 0 0 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: .16em;
  color: var(--sand);
}

.page-about .about-timeline__title {
  margin: 0 0 8px;
  font-size: clamp(17px, 1.9vw, 21px);
  font-weight: 400;
  letter-spacing: .02em;
  color: var(--white);
}

.page-about .about-timeline__text {
  margin: 0;
  max-width: 34em;
  font-size: 14px;
  line-height: 1.8;
  color: var(--mist);
}

/* ---------- 覆盖与场景 ---------- */

.page-about .about-scope {
  margin-top: clamp(26px, 3.6vw, 42px);
}

.page-about .about-scope__grid {
  display: grid;
  gap: 16px;
}

.page-about .about-scope__use {
  border: 1px solid var(--line);
  border-left: 3px solid var(--flame);
  border-radius: var(--about-radius);
  background: linear-gradient(150deg, rgba(18, 60, 48, .8) 0%, rgba(11, 43, 34, .45) 100%);
  padding: clamp(20px, 2.6vw, 28px);
  min-width: 0;
}

.page-about .about-scope__use .eyebrow {
  margin: 0 0 10px;
}

.page-about .about-scope__use-title {
  margin: 0 0 10px;
  font-size: clamp(18px, 2vw, 23px);
  font-weight: 400;
  line-height: 1.35;
  color: var(--white);
}

.page-about .about-scope__use-text {
  margin: 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--mist);
}

.page-about .about-next {
  margin-top: clamp(26px, 3.4vw, 40px);
  padding-top: clamp(22px, 2.8vw, 30px);
  border-top: 1px dashed var(--line-strong);
}

.page-about .about-next__lead {
  margin: 0 0 18px;
  font-size: 16px;
  line-height: 1.8;
  color: rgba(244, 247, 245, .86);
}

.page-about .about-next__links {
  list-style: none;
  margin: 0 0 18px;
  padding: 0;
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.page-about .about-next__links li {
  min-width: 0;
}

.page-about .about-next__note {
  margin: 0;
  max-width: 34em;
  font-size: 14px;
  line-height: 1.8;
  color: var(--mist);
}

.page-about .about-next__link {
  color: var(--flame-soft);
  text-decoration: underline;
  text-underline-offset: 3px;
  transition: color .24s var(--ease);
}

.page-about .about-next__link:hover,
.page-about .about-next__link:focus-visible {
  color: var(--flame);
}

/* ---------- 平板 ---------- */

@media (min-width: 700px) {
  .page-about .about-scope__grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .page-about .about-facts {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

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

  .page-about .about-timeline__card {
    padding: 20px 24px;
  }
}

@media (min-width: 760px) {
  .page-about .about-team {
    grid-template-columns: minmax(0, 3.6fr) minmax(0, 6.4fr);
    align-items: start;
  }

  .page-about .about-collab {
    grid-template-columns: minmax(0, 6fr) minmax(0, 4fr);
  }

  .page-about .about-collab__map {
    align-items: center;
  }
}

/* ---------- 桌面：粘性索引 + 内容流 ---------- */

@media (min-width: 1000px) {
  .page-about .about-layout {
    display: grid;
    grid-template-columns: minmax(180px, 2.4fr) minmax(0, 9.6fr);
    gap: clamp(36px, 5vw, 84px);
    align-items: start;
  }

  .page-about .about-index {
    position: sticky;
    top: calc(var(--head-h) + 28px);
    padding-bottom: 0;
    border-bottom: 0;
    margin-bottom: 0;
  }

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

  .page-about .about-index__list li + li {
    margin-top: 2px;
  }

  .page-about .about-index__link {
    display: flex;
    width: 100%;
    padding: 9px 0;
    border-bottom: 1px solid var(--line);
    font-size: 13px;
  }

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

  .page-about .about-chapter__head {
    align-items: baseline;
  }
}

@media (min-width: 1200px) {
  .page-about .about-index {
    top: calc(var(--head-h) + 44px);
  }

  .page-about .about-hero__title {
    max-width: 17ch;
  }
}

/* ---------- 无障碍：降低动效 ---------- */

@media (prefers-reduced-motion: reduce) {
  .page-about .about-bar__fill,
  .page-about .about-index__link,
  .page-about .about-next__link {
    transition: none;
  }
}

.page-about {
  --w: 1rem;
}