.page-about {
  display: block;
  padding-bottom: clamp(48px, 8vw, 104px);
}

/* ---------- 页首 ---------- */
.page-about .about-top {
  padding-top: clamp(22px, 4.5vw, 52px);
  padding-bottom: clamp(26px, 5vw, 54px);
  position: relative;
}

.page-about .about-top h1 {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(32px, 6.8vw, 68px);
  line-height: 1.06;
  letter-spacing: -0.012em;
  color: var(--paper);
  margin: 14px 0 0;
  max-width: 17ch;
}

.page-about .about-top .lede {
  margin-top: clamp(16px, 2.6vw, 26px);
  max-width: 38ch;
  color: var(--board);
  font-size: clamp(15px, 1.8vw, 18px);
  line-height: 1.72;
}

.page-about .about-note {
  margin-top: 16px;
  max-width: 36ch;
  font-family: var(--font-mono);
  font-size: 12.5px;
  letter-spacing: 0.04em;
  line-height: 1.85;
  color: var(--index);
}

.page-about .about-top::after {
  content: "";
  display: block;
  margin-top: clamp(24px, 4vw, 40px);
  height: 1px;
  background: linear-gradient(90deg, var(--clay) 0 22%, var(--line) 22% 100%);
}

/* ---------- 通用章节间距 ---------- */
.page-about .sec {
  margin-top: clamp(46px, 8vw, 96px);
}

.page-about .sec-head .sec-intro {
  margin-top: 14px;
  max-width: 36ch;
  color: var(--board);
}

/* ---------- 稳结构三定义 ---------- */
.page-about .define-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .define-item {
  background: var(--ink);
  padding: clamp(20px, 3.4vw, 30px) clamp(18px, 3vw, 28px) clamp(24px, 3.8vw, 34px);
  position: relative;
  transition: background var(--dur) var(--ease);
}

.page-about .define-item:hover {
  background: var(--layer);
}

.page-about .define-index {
  display: block;
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--pulse);
  margin-bottom: 14px;
}

.page-about .define-item h3 {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: clamp(18px, 2.2vw, 22px);
  color: var(--paper);
  margin: 0 0 10px;
  letter-spacing: 0.01em;
}

.page-about .define-item p {
  margin: 0;
  font-size: 14.5px;
  line-height: 1.72;
  color: var(--board);
  max-width: 30ch;
}

/* ---------- 来历 ---------- */
.page-about .statement-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(24px, 4vw, 48px);
  align-items: start;
}

.page-about .statement-body h2 {
  margin-bottom: 16px;
}

.page-about .statement-body .prose {
  margin: 0 0 15px;
  color: var(--paper);
  opacity: 0.88;
}

/* ---------- 时间线 ---------- */
.page-about .timeline-fig {
  margin-bottom: clamp(28px, 5vw, 48px);
}

.page-about .timeline {
  list-style: none;
  margin: 0;
  padding: 0 0 0 22px;
  border-left: 1px solid var(--line);
}

.page-about .timeline-item {
  position: relative;
}

.page-about .timeline-item::before {
  content: "";
  position: absolute;
  left: -27px;
  top: 30px;
  width: 9px;
  height: 9px;
  background: var(--ink);
  border: 1px solid var(--clay);
  transform: rotate(45deg);
  transition: background var(--dur) var(--ease), border-color var(--dur) var(--ease);
}

.page-about .timeline-item:hover::before,
.page-about .timeline-item:focus-within::before {
  background: var(--pulse);
  border-color: var(--pulse);
}

.page-about .tl-fold {
  border-bottom: 1px solid var(--line);
}

.page-about .tl-head {
  display: grid;
  grid-template-columns: 5.6ch 1fr auto;
  gap: 10px 14px;
  align-items: baseline;
  padding: clamp(16px, 2.6vw, 22px) 4px clamp(16px, 2.6vw, 22px) 0;
  cursor: pointer;
  list-style: none;
  transition: color var(--dur) var(--ease);
}

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

.page-about .tl-head:hover .tl-name,
.page-about .tl-fold[open] .tl-name {
  color: var(--pulse);
}

.page-about .tl-year {
  font-size: clamp(20px, 3.6vw, 30px);
  font-weight: 600;
  letter-spacing: 0.1em;
  color: var(--gold);
  line-height: 1;
}

.page-about .tl-name {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: clamp(16px, 2.2vw, 21px);
  color: var(--paper);
  transition: color var(--dur) var(--ease);
}

.page-about .tl-hint {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.1em;
  color: var(--index);
  white-space: nowrap;
}

.page-about .tl-fold[open] .tl-hint {
  color: var(--pulse);
}

.page-about .tl-body {
  padding: 2px 4px clamp(18px, 3vw, 26px) 0;
  animation: about-reveal var(--dur) var(--ease);
}

.page-about .tl-line {
  margin: 0 0 10px;
  max-width: 40ch;
  font-size: 14.5px;
  line-height: 1.75;
  color: var(--board);
  padding-left: 12px;
  border-left: 2px solid var(--clay);
}

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

@keyframes about-reveal {
  from { opacity: 0; transform: translateY(-4px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ---------- 三轨编号 ---------- */
.page-about .about-code {
  background: var(--layer);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  padding: clamp(30px, 5vw, 56px) clamp(18px, 4vw, 46px);
}

.page-about .about-code .sec-head {
  margin-bottom: clamp(22px, 3.6vw, 36px);
}

.page-about .code-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
}

.page-about .code-card {
  background: var(--ink);
  border: 1px solid var(--line);
  padding: clamp(18px, 3vw, 26px);
  outline: none;
  transition: border-color var(--dur) var(--ease), transform var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}

.page-about .code-card:hover,
.page-about .code-card:focus-visible {
  border-color: var(--pulse);
  transform: translateY(-3px);
  box-shadow: 0 10px 26px rgba(0, 0, 0, 0.34);
}

.page-about .code-sample {
  font-size: clamp(26px, 4.6vw, 38px);
  font-weight: 600;
  letter-spacing: 0.12em;
  color: var(--flash);
  margin: 14px 0 10px;
  line-height: 1;
  transition: color var(--dur) var(--ease);
}

.page-about .code-card:hover .code-sample,
.page-about .code-card:focus-visible .code-sample {
  color: var(--pulse);
}

.page-about .code-note {
  margin: 0;
  font-size: 14px;
  line-height: 1.72;
  color: var(--board);
  max-width: 30ch;
}

.page-about .code-foot {
  margin-top: clamp(22px, 3.4vw, 32px);
  color: var(--board);
}

.page-about .code-foot a,
.page-about .outro-line a,
.page-about .prose a {
  color: var(--pulse);
  text-decoration: none;
  border-bottom: 1px solid rgba(255, 106, 31, 0.42);
  transition: border-color var(--dur) var(--ease), color var(--dur) var(--ease);
}

.page-about .code-foot a:hover,
.page-about .outro-line a:hover,
.page-about .prose a:hover,
.page-about .code-foot a:focus-visible,
.page-about .outro-line a:focus-visible,
.page-about .prose a:focus-visible {
  color: var(--gold);
  border-bottom-color: var(--gold);
}

/* ---------- 来源与流程 ---------- */
.page-about .source-flow {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}

.page-about .flow-step {
  background: var(--ink);
  padding: clamp(18px, 3vw, 28px);
  position: relative;
  padding-right: clamp(36px, 5vw, 52px);
}

.page-about .flow-step::after {
  content: "";
  position: absolute;
  right: 16px;
  top: 50%;
  width: 10px;
  height: 1px;
  background: var(--clay);
}

.page-about .flow-num {
  display: block;
  font-size: 11px;
  letter-spacing: 0.16em;
  color: var(--gold);
  margin-bottom: 12px;
}

.page-about .flow-step h3 {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: clamp(16px, 2vw, 19px);
  color: var(--paper);
  margin: 0 0 8px;
}

.page-about .flow-step p {
  margin: 0;
  font-size: 14px;
  line-height: 1.72;
  color: var(--board);
  max-width: 34ch;
}

.page-about .source-note {
  margin-top: clamp(20px, 3.4vw, 32px);
  padding-left: 16px;
  border-left: 2px solid var(--clay);
}

.page-about .source-note .prose {
  margin: 0;
  color: var(--board);
}

/* ---------- 团队 ---------- */
.page-about .team-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: clamp(14px, 2.6vw, 22px);
}

.page-about .team-stat {
  border: 1px solid var(--line);
  border-top: 2px solid var(--clay);
  background: var(--ink);
  padding: clamp(18px, 3vw, 26px);
  transition: border-top-color var(--dur) var(--ease);
}

.page-about .team-stat:hover {
  border-top-color: var(--pulse);
}

.page-about .team-num {
  display: block;
  font-size: clamp(38px, 7vw, 56px);
  font-weight: 600;
  line-height: 1;
  letter-spacing: 0.06em;
  color: var(--paper);
}

.page-about .team-role {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 15px;
  color: var(--gold);
  margin: 14px 0 8px;
  letter-spacing: 0.03em;
}

.page-about .team-desc {
  margin: 0;
  font-size: 13.5px;
  line-height: 1.7;
  color: var(--board);
  max-width: 28ch;
}

.page-about .team-foot {
  margin-top: clamp(22px, 3.6vw, 34px);
  color: var(--board);
}

/* ---------- 自我约束 ---------- */
.page-about .rules-fig {
  margin-bottom: clamp(28px, 4.6vw, 44px);
}

.page-about .rules-stack {
  display: grid;
  grid-template-columns: 1fr;
  gap: 10px;
}

.page-about .rule-fold {
  border: 1px solid var(--line);
  background: var(--ink);
  transition: border-color var(--dur) var(--ease);
}

.page-about .rule-fold[open] {
  border-color: var(--clay);
  background: var(--layer);
}

.page-about .rule-head {
  display: grid;
  grid-template-columns: 3.2ch 1fr auto;
  gap: 12px;
  align-items: baseline;
  padding: clamp(15px, 2.4vw, 20px) clamp(16px, 2.6vw, 24px);
  cursor: pointer;
  list-style: none;
}

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

.page-about .rule-idx {
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--pulse);
}

.page-about .rule-name {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: clamp(15px, 2vw, 18px);
  color: var(--paper);
}

.page-about .rule-hint {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.1em;
  color: var(--index);
  white-space: nowrap;
}

.page-about .rule-fold[open] .rule-hint {
  color: var(--gold);
}

.page-about .rule-list {
  margin: 0;
  padding: 0 clamp(16px, 2.6vw, 24px) clamp(18px, 2.8vw, 24px) clamp(40px, 5vw, 52px);
  list-style: none;
  animation: about-reveal var(--dur) var(--ease);
}

.page-about .rule-list li {
  position: relative;
  font-size: 14px;
  line-height: 1.75;
  color: var(--board);
  padding-left: 14px;
  margin-bottom: 10px;
  max-width: 42ch;
}

.page-about .rule-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.72em;
  width: 5px;
  height: 1px;
  background: var(--clay);
}

.page-about .rule-list li:last-child {
  margin-bottom: 0;
}

/* ---------- 结尾指引 ---------- */
.page-about .about-outro {
  border-top: 1px solid var(--line);
  padding-top: clamp(22px, 3.6vw, 34px);
}

.page-about .outro-line {
  margin: 14px 0 0;
  max-width: 46ch;
  font-size: clamp(14.5px, 1.8vw, 16px);
  line-height: 1.8;
  color: var(--board);
}

/* ---------- 媒体查询 ---------- */
@media (min-width: 720px) {
  .page-about .define-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .page-about .statement-grid {
    grid-template-columns: minmax(0, 4fr) minmax(0, 7fr);
    gap: clamp(28px, 5vw, 56px);
  }

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

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

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

  .page-about .rules-stack {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 12px;
  }
}

@media (min-width: 1000px) {
  .page-about .about-top {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(0, 320px);
    column-gap: clamp(32px, 5vw, 72px);
    align-items: end;
  }

  .page-about .about-top .crumb {
    grid-column: 1 / -1;
  }

  .page-about .about-top h1,
  .page-about .about-top .eyebrow,
  .page-about .about-top .lede {
    grid-column: 1;
  }

  .page-about .about-note {
    grid-column: 2;
    grid-row: 3 / span 2;
    margin-top: 0;
    padding-left: 18px;
    border-left: 1px solid var(--line);
    align-self: end;
    max-width: none;
  }

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

  .page-about .timeline {
    padding-left: 34px;
  }

  .page-about .timeline-item::before {
    left: -39px;
  }

  .page-about .tl-head {
    padding-right: 18px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .tl-body,
  .page-about .rule-list {
    animation: none;
  }

  .page-about .code-card:hover,
  .page-about .code-card:focus-visible {
    transform: none;
  }
}