.page-about {
  --about-line: rgba(243, 236, 224, .13);
  --about-gap: clamp(26px, 5vw, 56px);
  display: block;
  background: var(--ink-950);
  color: var(--cream-50);
  overflow-x: clip;
}

.page-about .wrap {
  width: 100%;
  max-width: var(--shell);
  margin-inline: auto;
  padding-inline: var(--gut);
}

/* ---------- 面包屑 ---------- */
.page-about .about-crumb {
  padding-top: clamp(18px, 3vw, 32px);
}
.page-about .about-crumb ol {
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  margin: 0;
  padding: 0;
  list-style: none;
  font-size: 13px;
  letter-spacing: .02em;
  color: var(--text-dim);
}
.page-about .about-crumb li {
  display: flex;
  align-items: center;
}
.page-about .about-crumb li + li::before {
  content: "／";
  margin-inline: 8px;
  color: rgba(243, 236, 224, .3);
}
.page-about .about-crumb a {
  color: var(--text-dim);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color 180ms var(--ease), border-color 180ms var(--ease);
}
.page-about .about-crumb a:hover {
  color: var(--cyan-400);
  border-bottom-color: var(--cyan-700);
}
.page-about .about-crumb [aria-current="page"] {
  color: var(--cream-50);
}

/* ---------- 首屏 ---------- */
.page-about .hero {
  padding-block: clamp(26px, 4.4vw, 56px) clamp(34px, 5.6vw, 72px);
  background:
    radial-gradient(120% 80% at 88% 0%, rgba(53, 224, 210, .09), transparent 60%),
    radial-gradient(90% 70% at 0% 100%, rgba(196, 71, 42, .07), transparent 62%);
}
.page-about .hero-grid {
  display: grid;
  gap: clamp(30px, 5vw, 52px);
}
.page-about .hero-kicker {
  color: var(--cyan-400);
  margin: 0;
}
.page-about .hero-title {
  margin: 14px 0 0;
  font-size: clamp(32px, 6.4vw, 64px);
  font-weight: 400;
  line-height: 1.06;
  letter-spacing: -0.01em;
  color: var(--cream-50);
  max-width: 16em;
}
.page-about .hero-lede {
  margin: 20px 0 0;
  font-size: 17px;
  line-height: 1.85;
  color: rgba(243, 236, 224, .8);
  max-width: 34em;
}
.page-about .hero-note {
  margin: 18px 0 0;
  padding-left: 14px;
  border-left: 2px solid var(--cyan-700);
  font-size: 13px;
  line-height: 1.75;
  color: var(--text-dim);
  max-width: 38em;
}

.page-about .hero-visual {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
}
.page-about .gauge {
  position: relative;
  width: min(74vw, 340px);
  aspect-ratio: 1 / 1;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: radial-gradient(circle at 50% 50%, rgba(53, 224, 210, .1), transparent 64%);
}
.page-about .gauge-ring {
  position: absolute;
  inset: 0;
  border-radius: 50%;
  background: conic-gradient(from 205deg, var(--cyan-400) 0 51%, rgba(243, 236, 224, .09) 51% 100%);
  -webkit-mask: radial-gradient(circle at 50% 50%, transparent 61%, #000 61.5%);
  mask: radial-gradient(circle at 50% 50%, transparent 61%, #000 61.5%);
}
.page-about .gauge-ticks {
  position: absolute;
  inset: 6%;
  border-radius: 50%;
  background: repeating-conic-gradient(from 205deg, rgba(243, 236, 224, .55) 0 .6deg, transparent .6deg 7.5deg);
  -webkit-mask: radial-gradient(circle at 50% 50%, transparent 87%, #000 88%);
  mask: radial-gradient(circle at 50% 50%, transparent 87%, #000 88%);
  opacity: .5;
}
.page-about .gauge-core {
  position: relative;
  display: grid;
  justify-items: center;
  gap: 8px;
  text-align: center;
  padding-inline: 12%;
}
.page-about .gauge-num {
  font-family: var(--font-mono);
  font-size: clamp(56px, 13vw, 100px);
  line-height: 1;
  letter-spacing: .02em;
  color: var(--cream-50);
  font-variant-numeric: tabular-nums;
}
.page-about .gauge-label {
  font-size: 12px;
  letter-spacing: .16em;
  color: var(--text-dim);
}
.page-about .gauge-foot {
  margin: 0;
  font-size: 12px;
  letter-spacing: .06em;
  color: var(--text-dim);
  text-align: center;
}

/* ---------- 正文骨架 ---------- */
.page-about .about-body {
  display: grid;
  gap: clamp(26px, 4vw, 40px);
  padding-bottom: clamp(34px, 6vw, 72px);
}
.page-about .about-rail {
  order: -1;
}
.page-about .about-flow {
  min-width: 0;
}

/* ---------- 刻度索引 ---------- */
.page-about .rail-title {
  margin: 0 0 12px;
  color: var(--text-dim);
}
.page-about .rail-list {
  display: flex;
  gap: 10px;
  margin: 0;
  padding: 0 0 6px;
  list-style: none;
  overflow-x: auto;
  scrollbar-width: thin;
}
.page-about .rail-link {
  display: flex;
  align-items: baseline;
  gap: 8px;
  padding: 8px 13px;
  border: 1px solid var(--about-line);
  border-radius: var(--r-sm);
  color: var(--text-dim);
  text-decoration: none;
  font-size: 13px;
  letter-spacing: .02em;
  white-space: nowrap;
  transition: color 200ms var(--ease), border-color 200ms var(--ease);
}
.page-about .rail-link:hover {
  color: var(--cream-50);
  border-color: var(--line-dark-strong);
}
.page-about .rail-num {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .1em;
  color: inherit;
  opacity: .8;
}

.page-about:has(#scope.is-inview) .rail-link[href="#scope"],
.page-about:has(#taxonomy.is-inview) .rail-link[href="#taxonomy"],
.page-about:has(#twolines.is-inview) .rail-link[href="#twolines"],
.page-about:has(#stages.is-inview) .rail-link[href="#stages"],
.page-about:has(#review.is-inview) .rail-link[href="#review"],
.page-about:has(#cadence.is-inview) .rail-link[href="#cadence"] {
  color: var(--cyan-400);
  border-color: var(--cyan-700);
}

/* ---------- 章节 ---------- */
.page-about .chapter {
  padding-block: clamp(30px, 5vw, 56px);
  border-top: 1px solid var(--about-line);
}
.page-about .about-flow > .chapter:first-child {
  border-top: 0;
  padding-top: 0;
}
.page-about .chapter-head {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  column-gap: clamp(12px, 2.2vw, 26px);
  row-gap: 10px;
  margin: 0 0 clamp(20px, 3vw, 34px);
  scroll-margin-top: 96px;
}
.page-about .chapter-num {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .18em;
  color: rgba(243, 236, 224, .42);
  padding-top: .72em;
  transition: color 240ms var(--ease);
}
.page-about .chapter-head.is-inview .chapter-num {
  color: var(--cyan-400);
}
.page-about .chapter-title {
  margin: 0;
  font-size: clamp(24px, 4.2vw, 40px);
  font-weight: 400;
  line-height: 1.14;
  letter-spacing: -0.01em;
  color: var(--cream-50);
}
.page-about .chapter-note {
  grid-column: 2;
  margin: 0;
  font-size: 13px;
  line-height: 1.7;
  color: var(--text-dim);
}
.page-about .chapter-body > p {
  margin: 0 0 16px;
  font-size: 16px;
  line-height: 1.85;
  color: rgba(243, 236, 224, .8);
  max-width: 44em;
}
.page-about .chapter-body > p:last-child {
  margin-bottom: 0;
}
.page-about .scope-foot {
  margin: 20px 0 0;
  padding-left: 14px;
  border-left: 2px solid var(--cyan-700);
  font-size: 13px;
  line-height: 1.75;
  color: var(--text-dim);
  max-width: 44em;
}

/* ---------- 01 边界清单 ---------- */
.page-about .scope-grid {
  display: grid;
  gap: 16px;
  margin: 24px 0 0;
}
.page-about .scope-card {
  padding: clamp(18px, 2.6vw, 26px);
  border: 1px solid var(--about-line);
  border-radius: var(--r-md);
  background: linear-gradient(180deg, rgba(20, 48, 74, .5), rgba(8, 19, 31, .2));
}
.page-about .scope-card--keep {
  background: var(--cream-50);
  border-color: var(--line-print);
  color: var(--brown-900);
}
.page-about .scope-card--keep .label {
  color: var(--ember-500);
}
.page-about .scope-card--drop {
  border-left: 3px solid var(--ember-500);
}
.page-about .scope-card--drop .label {
  color: var(--cyan-400);
}
.page-about .scope-list {
  margin: 14px 0 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 11px;
}
.page-about .scope-list li {
  position: relative;
  padding-left: 18px;
  font-size: 15px;
  line-height: 1.72;
}
.page-about .scope-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: .74em;
  width: 8px;
  height: 1px;
  background: currentColor;
  opacity: .55;
}
.page-about .scope-card--keep .scope-list li {
  color: var(--brown-900);
}
.page-about .scope-card--drop .scope-list li {
  color: rgba(243, 236, 224, .82);
}

/* ---------- 02 选项卡 ---------- */
.page-about .tabset {
  position: relative;
  margin-top: 26px;
}
.page-about .tab-radio {
  position: absolute;
  width: 1px;
  height: 1px;
  opacity: 0;
  pointer-events: none;
}
.page-about .tab-labels {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 18px;
}
.page-about .tab-label {
  display: inline-flex;
  align-items: center;
  padding: 9px 15px;
  font-size: 13px;
  letter-spacing: .04em;
  color: var(--text-dim);
  border: 1px solid var(--about-line);
  border-radius: var(--r-sm);
  background: rgba(11, 27, 43, .5);
  cursor: pointer;
  transition: color 180ms var(--ease), border-color 180ms var(--ease), background 180ms var(--ease);
}
.page-about .tab-label:hover {
  color: var(--cream-50);
  border-color: var(--line-dark-strong);
}
.page-about .tab-panels {
  position: relative;
}
.page-about .tab-panel {
  display: none;
  padding: clamp(18px, 2.6vw, 28px);
  border: 1px solid var(--about-line);
  border-left: 3px solid var(--cyan-700);
  border-radius: var(--r-md);
  background: rgba(20, 48, 74, .36);
}
.page-about .tab-panel h3 {
  margin: 0 0 12px;
  font-size: 18px;
  font-weight: 500;
  letter-spacing: .01em;
  color: var(--cream-50);
}
.page-about .tab-panel p {
  margin: 0 0 12px;
  font-size: 15px;
  line-height: 1.82;
  color: rgba(243, 236, 224, .78);
  max-width: 42em;
}
.page-about .tab-panel .panel-data {
  margin: 0;
  padding-top: 12px;
  border-top: 1px dashed var(--about-line);
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .05em;
  color: var(--cyan-400);
}

.page-about #tab-rules:checked ~ .tab-panels #panel-rules,
.page-about #tab-device:checked ~ .tab-panels #panel-device,
.page-about #tab-service:checked ~ .tab-panels #panel-service,
.page-about #tab-budget:checked ~ .tab-panels #panel-budget {
  display: block;
}
.page-about #tab-rules:checked ~ .tab-labels [for="tab-rules"],
.page-about #tab-device:checked ~ .tab-labels [for="tab-device"],
.page-about #tab-service:checked ~ .tab-labels [for="tab-service"],
.page-about #tab-budget:checked ~ .tab-labels [for="tab-budget"] {
  color: var(--ink-950);
  background: var(--cyan-400);
  border-color: var(--cyan-400);
}
.page-about #tab-rules:focus-visible ~ .tab-labels [for="tab-rules"],
.page-about #tab-device:focus-visible ~ .tab-labels [for="tab-device"],
.page-about #tab-service:focus-visible ~ .tab-labels [for="tab-service"],
.page-about #tab-budget:focus-visible ~ .tab-labels [for="tab-budget"] {
  outline: 2px solid var(--cyan-400);
  outline-offset: 2px;
}

/* ---------- 图版 ---------- */
.page-about .media-frame {
  margin: clamp(22px, 3.4vw, 36px) 0;
  border: 1px solid var(--about-line);
  border-radius: var(--r-md);
  overflow: hidden;
  background: var(--ink-900);
}
.page-about .media-frame img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
}
.page-about .media-caption {
  margin: 0;
  padding: 12px 16px;
  border-top: 1px solid var(--about-line);
  font-size: 13px;
  line-height: 1.7;
  color: var(--text-dim);
}

/* ---------- 03 两条线 ---------- */
.page-about .line-grid {
  display: grid;
  gap: 16px;
  margin: 24px 0 0;
}
.page-about .line-card {
  padding: clamp(18px, 2.6vw, 26px);
  border: 1px solid var(--about-line);
  border-radius: var(--r-md);
  background: rgba(20, 48, 74, .34);
}
.page-about .line-card--cyan {
  border-top: 3px solid var(--cyan-400);
}
.page-about .line-card--cyan .label {
  color: var(--cyan-400);
}
.page-about .line-card--cream {
  background: var(--cream-50);
  border-color: var(--line-print);
  border-top: 3px solid var(--amber-600);
  color: var(--brown-900);
}
.page-about .line-card--cream .label {
  color: var(--amber-600);
}
.page-about .line-count {
  display: block;
  margin: 6px 0 14px;
  font-family: var(--font-mono);
  font-size: clamp(30px, 5vw, 46px);
  line-height: 1;
  letter-spacing: .02em;
  color: var(--cyan-400);
  font-variant-numeric: tabular-nums;
}
.page-about .line-card--cream .line-count {
  color: var(--ember-500);
}
.page-about .line-card p:last-child {
  margin: 0;
  font-size: 15px;
  line-height: 1.82;
}
.page-about .line-card--cyan p:last-child {
  color: rgba(243, 236, 224, .78);
}
.page-about .line-card--cream p:last-child {
  color: var(--brown-900);
}

/* ---------- 04 阶段轨道 ---------- */
.page-about .stage-track {
  display: flex;
  gap: 14px;
  margin: 24px 0 0;
  padding: 4px 0 14px;
  list-style: none;
  overflow-x: auto;
  scroll-snap-type: x mandatory;
  scrollbar-width: thin;
}
.page-about .stage {
  flex: 0 0 76%;
  scroll-snap-align: start;
  display: flex;
  flex-direction: column;
  padding: 18px 16px 20px;
  border: 1px solid var(--about-line);
  border-radius: var(--r-sm);
  background: linear-gradient(180deg, rgba(20, 48, 74, .46), rgba(11, 27, 43, .12));
  transition: transform 160ms var(--ease), border-color 160ms var(--ease);
}
.page-about .stage:hover {
  transform: translateY(-2px);
  border-color: var(--line-dark-strong);
}
.page-about .stage-bar {
  display: block;
  height: 3px;
  margin-bottom: 16px;
  border-radius: 2px;
  background: linear-gradient(90deg, var(--cyan-700), var(--cyan-400));
}
.page-about .stage:nth-child(1) .stage-bar { width: 28%; }
.page-about .stage:nth-child(2) .stage-bar { width: 40%; }
.page-about .stage:nth-child(3) .stage-bar { width: 52%; }
.page-about .stage:nth-child(4) .stage-bar { width: 64%; }
.page-about .stage:nth-child(5) .stage-bar { width: 76%; }
.page-about .stage:nth-child(6) .stage-bar { width: 88%; }
.page-about .stage:nth-child(7) .stage-bar { width: 100%; }
.page-about .stage-meta {
  display: flex;
  align-items: baseline;
  gap: 10px;
  margin: 0;
}
.page-about .stage-idx {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .18em;
  color: rgba(243, 236, 224, .45);
}
.page-about .stage-year {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .08em;
  color: var(--cyan-400);
}
.page-about .stage-title {
  margin: 10px 0 6px;
  font-size: 18px;
  font-weight: 500;
  line-height: 1.35;
  color: var(--cream-50);
}
.page-about .stage-desc {
  margin: 0 0 16px;
  font-size: 14px;
  line-height: 1.75;
  color: rgba(243, 236, 224, .72);
}
.page-about .stage-issue {
  align-self: flex-start;
  margin-top: auto;
  padding: 3px 9px;
  font-size: 11px;
  letter-spacing: .1em;
  color: var(--cream-50);
  background: var(--ember-500);
  border-radius: var(--r-sm);
}

/* ---------- 05 审校阶梯 ---------- */
.page-about .stair {
  display: grid;
  gap: 14px;
  margin-top: 6px;
}
.page-about .step {
  padding: clamp(18px, 2.4vw, 24px);
  border: 1px solid var(--about-line);
  border-top: 2px solid var(--cyan-700);
  border-radius: var(--r-sm);
  background: rgba(11, 27, 43, .72);
  transition: border-color 180ms var(--ease), transform 160ms var(--ease);
}
.page-about .step:hover,
.page-about .step:focus-within {
  border-color: var(--cyan-400);
  transform: translateY(-2px);
}
.page-about .step-idx {
  margin: 0 0 8px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: .18em;
  color: var(--cyan-400);
}
.page-about .step-title {
  margin: 0 0 8px;
  font-size: 18px;
  font-weight: 500;
  color: var(--cream-50);
}
.page-about .step-desc {
  margin: 0;
  font-size: 15px;
  line-height: 1.78;
  color: rgba(243, 236, 224, .78);
}
.page-about .step-extra {
  margin: 14px 0 0;
  padding-top: 11px;
  border-top: 1px dashed var(--about-line);
  font-size: 13px;
  line-height: 1.7;
  color: var(--text-dim);
  transition: color 180ms var(--ease);
}
.page-about .step:hover .step-extra,
.page-about .step:focus-within .step-extra {
  color: var(--cyan-400);
}

.page-about .team-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin-top: 22px;
  border: 1px solid var(--line-print);
  border-radius: var(--r-sm);
  background: var(--line-print);
  overflow: hidden;
}
.page-about .team-cell {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 20px 18px;
  background: var(--cream-50);
  color: var(--brown-900);
}
.page-about .team-cell--total {
  background: var(--cream-100);
}
.page-about .team-num {
  font-family: var(--font-mono);
  font-size: 34px;
  line-height: 1;
  letter-spacing: .02em;
  color: var(--brown-900);
  font-variant-numeric: tabular-nums;
}
.page-about .team-cell--total .team-num {
  color: var(--ember-500);
}
.page-about .team-label {
  font-size: 13px;
  letter-spacing: .06em;
  color: var(--brown-500);
}

/* ---------- 06 更新节奏 ---------- */
.page-about .cadence-list {
  margin: 24px 0 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--about-line);
}
.page-about .cadence-item {
  display: grid;
  gap: 6px;
  padding: 18px 0;
  border-bottom: 1px solid var(--about-line);
}
.page-about .cadence-when {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .06em;
  color: var(--cyan-400);
}
.page-about .cadence-what {
  margin: 0;
  font-size: 15px;
  line-height: 1.78;
  color: rgba(243, 236, 224, .8);
  max-width: 42em;
}

/* ---------- 延伸入口带 ---------- */
.page-about .extend-band {
  display: flex;
  gap: 12px;
  margin-top: clamp(26px, 4vw, 44px);
  padding-bottom: 8px;
  overflow-x: auto;
  scroll-snap-type: x mandatory;
  scrollbar-width: thin;
}
.page-about .extend-cell {
  flex: 0 0 auto;
  min-width: 210px;
  scroll-snap-align: start;
  display: flex;
  flex-direction: column;
  gap: 7px;
  padding: 15px 17px;
  border: 1px solid var(--about-line);
  border-radius: var(--r-sm);
  background: rgba(20, 48, 74, .34);
  text-decoration: none;
  transition: border-color 180ms var(--ease), transform 160ms var(--ease), background 180ms var(--ease);
}
.page-about .extend-cell:hover {
  border-color: var(--cyan-400);
  background: rgba(20, 48, 74, .58);
  transform: translateY(-2px);
}
.page-about .extend-cell .data-key {
  font-size: 12px;
  letter-spacing: .16em;
  color: var(--cyan-400);
}
.page-about .extend-cell .data-val {
  font-size: 14px;
  line-height: 1.6;
  color: rgba(243, 236, 224, .78);
}

/* ---------- 断点 ---------- */
@media (min-width: 720px) {
  .page-about .scope-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 22px;
  }
  .page-about .line-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 22px;
  }
  .page-about .stage {
    flex: 0 0 44%;
  }
  .page-about .cadence-item {
    grid-template-columns: 168px minmax(0, 1fr);
    align-items: baseline;
    gap: 22px;
  }
  .page-about .team-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

@media (min-width: 900px) {
  .page-about .hero-grid {
    grid-template-columns: 6fr 4fr;
    align-items: center;
    gap: clamp(32px, 5vw, 72px);
  }
  .page-about .hero-visual {
    align-items: flex-end;
  }
  .page-about .gauge-foot {
    text-align: right;
  }
  .page-about .stair {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 18px;
    align-items: start;
  }
  .page-about .step:nth-child(2) {
    margin-top: 34px;
  }
  .page-about .step:nth-child(3) {
    margin-top: 68px;
  }
  .page-about .stage {
    flex: 0 0 31%;
  }
}

@media (min-width: 960px) {
  .page-about .about-body {
    grid-template-columns: minmax(0, 1fr) 202px;
    gap: clamp(32px, 5vw, 72px);
    align-items: start;
  }
  .page-about .about-rail {
    order: 0;
    position: sticky;
    top: 92px;
  }
  .page-about .rail-list {
    display: block;
    overflow: visible;
  }
  .page-about .rail-list > li + li {
    margin-top: 2px;
  }
  .page-about .rail-link {
    border: 0;
    border-left: 2px solid var(--about-line);
    border-radius: 0;
    padding: 9px 0 9px 14px;
    white-space: normal;
    line-height: 1.5;
  }
  .page-about .rail-link:hover {
    border-left-color: var(--line-dark-strong);
  }
  .page-about:has(#scope.is-inview) .rail-link[href="#scope"],
  .page-about:has(#taxonomy.is-inview) .rail-link[href="#taxonomy"],
  .page-about:has(#twolines.is-inview) .rail-link[href="#twolines"],
  .page-about:has(#stages.is-inview) .rail-link[href="#stages"],
  .page-about:has(#review.is-inview) .rail-link[href="#review"],
  .page-about:has(#cadence.is-inview) .rail-link[href="#cadence"] {
    border-left-color: var(--cyan-400);
  }
}

@media (min-width: 1180px) {
  .page-about .stage {
    flex: 0 0 23.4%;
  }
}

@media (prefers-reduced-motion: reduce) {
  .page-about .stage,
  .page-about .step,
  .page-about .extend-cell,
  .page-about .rail-link,
  .page-about .chapter-num {
    transition: none;
  }
  .page-about .stage:hover,
  .page-about .step:hover,
  .page-about .extend-cell:hover {
    transform: none;
  }
}