.page-about {
  position: relative;
  overflow-x: hidden;
  background-color: var(--ink-900);
  background-image:
    linear-gradient(var(--line-soft) 1px, transparent 1px),
    linear-gradient(90deg, var(--line-soft) 1px, transparent 1px);
  background-size: 64px 64px;
  color: var(--paper);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.75;
  padding-bottom: clamp(48px, 8vw, 96px);
}

.page-about .breadcrumb {
  margin-top: clamp(16px, 3vw, 28px);
}

/* ---------- 章节目录刻度条 ---------- */
.page-about .arc-toc {
  display: none;
}

/* ---------- 首屏 ---------- */
.page-about .arc-hero {
  position: relative;
  padding: clamp(24px, 5vw, 56px) 0 clamp(28px, 5vw, 56px);
  border-bottom: 1px solid var(--line);
}

.page-about .arc-hero::before {
  content: "";
  position: absolute;
  top: -30%;
  right: -20%;
  width: min(760px, 62%);
  height: 170%;
  background: linear-gradient(150deg, var(--amber-soft), rgba(58, 160, 255, 0.08) 55%, transparent 78%);
  clip-path: polygon(32% 0, 100% 0, 68% 100%, 0 100%);
  pointer-events: none;
  z-index: 0;
}

.page-about .arc-hero > * {
  position: relative;
  z-index: 1;
}

.page-about .arc-hero h1 {
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(28px, 5.4vw, 60px);
  line-height: 1.08;
  letter-spacing: -0.005em;
  color: var(--white);
  margin: 14px 0 0;
  max-width: 16em;
}

.page-about .arc-hero .lede {
  margin-top: clamp(16px, 2.4vw, 26px);
  max-width: 62ch;
  font-size: clamp(15px, 1.6vw, 18px);
  line-height: 1.85;
  color: var(--paper);
}

.page-about .arc-stats {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: clamp(24px, 4vw, 40px) 0 0;
  padding: 0;
  list-style: none;
  background-color: var(--line);
  border: 1px solid var(--line);
}

.page-about .arc-stat {
  background-color: var(--ink-800);
  padding: 14px 16px 16px;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.page-about .arc-stat .data-figure {
  font-size: clamp(26px, 4.6vw, 44px);
  line-height: 1;
}

.page-about .arc-stat__label {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  color: var(--moss);
}

/* ---------- 章节骨架 ---------- */
.page-about .arc-section {
  padding-top: clamp(40px, 7vw, 88px);
}

.page-about .arc-section__head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 8px 22px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--line);
  margin-bottom: clamp(20px, 3vw, 34px);
}

.page-about .arc-section__head h2 {
  font-family: var(--font-serif);
  font-weight: 500;
  font-size: clamp(22px, 3.2vw, 36px);
  line-height: 1.25;
  letter-spacing: 0.01em;
  color: var(--white);
  margin: 0;
}

.page-about .arc-prose {
  max-width: 74ch;
}

.page-about .arc-prose .prose p {
  margin: 0 0 1.15em;
}

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

/* ---------- 时间线 ---------- */
.page-about .arc-media {
  margin: 0 0 clamp(22px, 3vw, 34px);
}

.page-about .arc-scale {
  display: grid;
  grid-template-columns: repeat(7, minmax(0, 1fr));
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.1em;
  color: var(--moss);
}

.page-about .arc-scale__tick {
  padding: 6px 0 6px 8px;
  border-left: 1px solid var(--line);
}

.page-about .arc-scale__tick:first-child {
  border-left-color: var(--amber-line);
  color: var(--amber);
}

.page-about .arc-timeline {
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: 76%;
  gap: 20px;
  position: relative;
  margin-top: 34px;
  padding: 0 0 14px;
  overflow-x: auto;
  scroll-snap-type: x proximity;
  -webkit-overflow-scrolling: touch;
}

.page-about .arc-timeline::before {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  top: 20px;
  height: 1px;
  background-color: var(--line);
}

.page-about .arc-node {
  position: relative;
  scroll-snap-align: start;
  padding-top: 30px;
}

.page-about .arc-node::before {
  content: "";
  position: absolute;
  left: 0;
  top: 16px;
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background-color: var(--amber);
  box-shadow: 0 0 0 4px var(--amber-soft);
  transition: transform 0.24s ease, box-shadow 0.24s ease;
}

.page-about .arc-node:hover::before,
.page-about .arc-node:focus-within::before {
  transform: scale(1.25);
  box-shadow: 0 0 0 8px var(--amber-soft);
}

.page-about .arc-node__year {
  display: block;
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.14em;
  color: var(--amber);
}

.page-about .arc-node__title {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 16px;
  line-height: 1.4;
  color: var(--white);
  margin: 8px 0 6px;
}

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

/* ---------- 团队 ---------- */
.page-about .arc-team {
  display: grid;
  gap: clamp(20px, 3vw, 36px);
  margin-bottom: clamp(28px, 4vw, 44px);
}

.page-about .arc-team__lead {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.page-about .arc-team__lead .data-figure {
  font-size: clamp(64px, 15vw, 132px);
  line-height: 0.9;
}

.page-about .arc-team__note {
  margin: 0;
  max-width: 40ch;
  font-size: 14px;
  line-height: 1.8;
  color: var(--moss);
}

.page-about .arc-team__media {
  margin: 0;
}

.page-about .arc-roles {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1px;
  margin: 0;
  padding: 0;
  list-style: none;
  background-color: var(--line);
  border: 1px solid var(--line);
}

.page-about .arc-role {
  background-color: var(--ink-800);
  padding: 20px 18px 22px;
  display: grid;
  grid-template-columns: 58px minmax(0, 1fr);
  gap: 4px 14px;
  align-items: start;
  transition: background-color 0.24s ease;
}

.page-about .arc-role:hover {
  background-color: var(--ink-700);
}

.page-about .arc-role__num {
  grid-row: span 2;
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  font-size: 42px;
  line-height: 1;
  color: var(--amber);
}

.page-about .arc-role:nth-child(2n) .arc-role__num {
  color: var(--blue);
}

.page-about .arc-role__label {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 15px;
  line-height: 1.5;
  color: var(--white);
}

.page-about .arc-role__desc {
  margin: 0;
  grid-column: 2;
  font-size: 13px;
  line-height: 1.75;
  color: var(--moss);
}

/* ---------- 流程 ---------- */
.page-about .arc-flow {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
  margin: 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--line);
}

.page-about .arc-step {
  position: relative;
  padding: 22px 0 22px 58px;
  border-bottom: 1px solid var(--line);
}

.page-about .arc-step__idx {
  position: absolute;
  left: 0;
  top: 22px;
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.12em;
  color: var(--amber);
}

.page-about .arc-step__title {
  margin: 0 0 6px;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 17px;
  line-height: 1.4;
  color: var(--white);
}

.page-about .arc-step__text {
  margin: 0;
  max-width: 62ch;
  font-size: 14px;
  line-height: 1.8;
  color: var(--moss);
}

/* ---------- 合作 ---------- */
.page-about .arc-partners {
  display: grid;
  gap: 1px;
  background-color: var(--line);
  border: 1px solid var(--line);
}

.page-about .arc-partners__panel {
  border: 0;
  border-radius: 0;
  padding: 24px 20px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  justify-content: flex-end;
  background-color: var(--ink-800);
}

.page-about .arc-partners__panel .data-figure {
  font-size: clamp(44px, 9vw, 84px);
  line-height: 0.95;
}

.page-about .arc-partners__label {
  margin: 0;
  font-size: 13px;
  line-height: 1.7;
  color: var(--moss);
}

.page-about .arc-partners__list {
  border: 0;
  border-radius: 0;
  padding: 24px 20px;
  background-color: var(--ink-900);
}

.page-about .arc-partners__list h3 {
  margin: 0 0 14px;
  font-family: var(--font-serif);
  font-weight: 500;
  font-size: 18px;
  color: var(--white);
}

.page-about .arc-partners__list ul {
  margin: 0;
  padding: 0;
  list-style: none;
}

.page-about .arc-partners__list li {
  position: relative;
  padding-left: 18px;
  margin-bottom: 10px;
  font-size: 14px;
  line-height: 1.8;
  color: var(--paper);
}

.page-about .arc-partners__list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.78em;
  width: 10px;
  height: 1px;
  background-color: var(--amber);
}

/* ---------- 读者 ---------- */
.page-about .arc-readers__lede {
  margin: 0 0 clamp(20px, 3vw, 30px);
  max-width: 66ch;
  font-size: 15px;
  line-height: 1.85;
  color: var(--moss);
}

.page-about .arc-readers {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1px;
  background-color: var(--line);
  border: 1px solid var(--line);
}

.page-about .arc-reader {
  background-color: var(--ink-800);
  padding: 24px 20px 22px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.page-about .arc-reader h3 {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 16px;
  line-height: 1.5;
  color: var(--white);
}

.page-about .arc-reader p {
  margin: 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--moss);
}

.page-about .arc-reader .crossref {
  margin-top: auto;
  align-self: flex-start;
  padding-top: 6px;
}

/* ---------- 计划 ---------- */
.page-about .arc-plan {
  display: grid;
  gap: clamp(22px, 3vw, 38px);
}

.page-about .arc-plan__media {
  margin: 0;
}

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

.page-about .arc-plan__list li {
  border-top: 1px solid var(--line);
  padding: 16px 0 18px;
}

.page-about .arc-plan__list li:first-child {
  border-top-color: var(--amber-line);
}

.page-about .arc-plan__list h3 {
  margin: 0 0 6px;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 16px;
  line-height: 1.5;
  color: var(--white);
}

.page-about .arc-plan__list p {
  margin: 0;
  font-size: 14px;
  line-height: 1.8;
  color: var(--moss);
}

.page-about .arc-plan__note {
  margin: 18px 0 0;
  padding-left: 14px;
  border-left: 2px solid var(--amber);
  font-size: 14px;
  line-height: 1.8;
  color: var(--paper);
}

/* ---------- 结尾行动区 ---------- */
.page-about .arc-cta {
  padding-top: clamp(44px, 7vw, 88px);
}

.page-about .arc-cta__inner {
  position: relative;
  border: 1px solid var(--line);
  background-color: var(--ink-800);
  background-image: linear-gradient(120deg, var(--blue-soft), transparent 62%);
  padding: clamp(24px, 4vw, 48px);
  overflow: hidden;
}

.page-about .arc-cta__inner::after {
  content: "";
  position: absolute;
  right: -14%;
  bottom: -60%;
  width: min(460px, 60%);
  height: 190%;
  background: linear-gradient(150deg, var(--amber-soft), transparent 72%);
  clip-path: polygon(38% 0, 100% 0, 62% 100%, 0 100%);
  pointer-events: none;
}

.page-about .arc-cta__inner > * {
  position: relative;
  z-index: 1;
}

.page-about .arc-cta__inner h2 {
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(22px, 3.4vw, 38px);
  line-height: 1.2;
  color: var(--white);
  margin: 12px 0 10px;
  max-width: 20em;
}

.page-about .arc-cta__inner p {
  margin: 0;
  max-width: 62ch;
  font-size: 15px;
  line-height: 1.8;
  color: var(--moss);
}

.page-about .arc-cta__actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: clamp(18px, 3vw, 28px);
}

/* ---------- 断点 ---------- */
@media (min-width: 641px) {
  .page-about .arc-stats {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }

  .page-about .arc-timeline {
    grid-auto-columns: 46%;
  }

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

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

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

  .page-about .arc-partners__list {
    grid-column: 1 / -1;
  }
}

@media (min-width: 901px) {
  .page-about .arc-timeline {
    grid-auto-flow: row;
    grid-auto-columns: auto;
    grid-template-columns: repeat(7, minmax(0, 1fr));
    gap: 18px;
    overflow-x: visible;
    padding-bottom: 0;
  }

  .page-about .arc-node {
    padding-top: 26px;
  }

  .page-about .arc-team {
    grid-template-columns: 0.85fr 1.15fr;
    align-items: end;
  }

  .page-about .arc-team__media {
    margin-bottom: 4px;
  }

  .page-about .arc-flow {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    column-gap: clamp(24px, 4vw, 56px);
  }

  .page-about .arc-step {
    padding-left: 62px;
  }

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

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

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

  .page-about .arc-partners__list {
    grid-column: auto;
  }

  .page-about .arc-plan {
    grid-template-columns: 0.75fr 1.25fr;
    align-items: start;
  }
}

@media (min-width: 1280px) {
  .page-about .arc-toc {
    display: flex;
    flex-direction: column;
    gap: 12px;
    position: fixed;
    right: 16px;
    top: 50%;
    transform: translateY(-50%);
    z-index: 30;
    padding: 10px 10px 10px 14px;
    border-left: 1px solid var(--line);
  }

  .page-about .arc-toc__link {
    font-family: var(--font-mono);
    font-size: 11px;
    letter-spacing: 0.12em;
    color: var(--moss);
    text-decoration: none;
    transition: color 0.2s ease, transform 0.2s ease;
  }

  .page-about .arc-toc__link:hover,
  .page-about .arc-toc__link.is-active {
    color: var(--amber);
    transform: translateX(-3px);
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .arc-node::before,
  .page-about .arc-role,
  .page-about .arc-toc__link {
    transition: none;
  }

  .page-about .arc-node:hover::before,
  .page-about .arc-node:focus-within::before {
    transform: none;
  }

  .page-about .arc-toc__link:hover,
  .page-about .arc-toc__link.is-active {
    transform: none;
  }
}