.page-about {
  --about-axis-w: 168px;
  --about-line: var(--ink-700);
  display: block;
  background: var(--ink-950);
  color: var(--body-text);
}

.page-about [hidden] {
  display: none !important;
}

/* ============ 首屏 ============ */
.page-about .about-hero {
  position: relative;
  overflow: hidden;
  padding: 26px 0 36px;
  background: linear-gradient(158deg, var(--ink-900) 0 44%, var(--ink-950) 44% 100%);
  border-bottom: 1px solid var(--about-line);
}

.page-about .about-hero::before {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  width: min(48%, 420px);
  height: 100%;
  background: linear-gradient(180deg, rgba(23, 196, 214, 0.10), rgba(23, 196, 214, 0));
  clip-path: polygon(28% 0, 100% 0, 100% 100%, 0 64%);
  pointer-events: none;
}

.page-about .about-hero::after {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  height: 3px;
  background: linear-gradient(
    90deg,
    var(--cyan-500) 0 26%,
    var(--blue-600) 26% 48%,
    transparent 48%
  );
}

.page-about .about-hero__inner {
  position: relative;
  z-index: 1;
}

.page-about .breadcrumbs {
  font-size: 13px;
  margin-bottom: 2px;
}

.page-about .about-hero__kicker {
  margin: 16px 0 0;
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--cyan-500);
}

.page-about .about-hero__title {
  margin: 10px 0 0;
  max-width: 20em;
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(28px, 6.4vw, 44px);
  line-height: 1.18;
  letter-spacing: -0.02em;
  color: var(--paper-050);
}

.page-about .about-hero__lede {
  max-width: 34em;
  margin: 16px 0 0;
}

.page-about .about-facts {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 28px 0 0;
  padding: 0;
  list-style: none;
  background: var(--about-line);
  border: 1px solid var(--about-line);
}

.page-about .about-facts__item {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 15px 16px;
  background: var(--ink-900);
}

.page-about .about-facts__num {
  font-size: 21px;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--cyan-500);
}

.page-about .about-facts__label {
  font-size: 13px;
  line-height: 1.5;
  color: var(--slate-400);
}

/* ============ 主轴与刻度 ============ */
.page-about .about-body {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 26px;
  padding: 28px 0 64px;
}

.page-about .about-axis {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  padding: 0 0 16px;
  border-bottom: 1px solid var(--about-line);
}

.page-about .about-axis__title {
  display: none;
}

.page-about .about-axis__item {
  display: inline-flex;
  align-items: baseline;
  gap: 7px;
  padding: 6px 10px;
  border: 1px solid var(--about-line);
  background: var(--ink-900);
  color: var(--slate-400);
  font-size: 13px;
  line-height: 1.4;
  text-decoration: none;
  transition: color 0.18s var(--ease), border-color 0.18s var(--ease),
    background-color 0.18s var(--ease);
}

.page-about .about-axis__item:hover,
.page-about .about-axis__item:focus-visible {
  color: var(--blue-300);
  border-color: var(--blue-300);
}

.page-about .about-axis__idx {
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--cyan-500);
}

.page-about .about-axis__item.is-current {
  color: var(--cyan-500);
  border-color: var(--cyan-500);
  background: rgba(23, 196, 214, 0.08);
}

.page-about .about-axis__item.is-current .about-axis__name {
  color: var(--cyan-500);
}

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

/* ============ 章节面板 ============ */
.page-about .about-chapter {
  position: relative;
  margin: 0 0 40px;
  padding: 26px 20px 30px;
  border: 1px solid var(--about-line);
  background: var(--ink-900);
  box-shadow: 12px 12px 0 -1px rgba(28, 40, 54, 0.75);
}

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

.page-about .about-chapter__no {
  position: absolute;
  top: 0;
  right: 16px;
  transform: translateY(-50%);
  padding: 3px 8px;
  font-size: 11px;
  letter-spacing: 0.12em;
  color: var(--slate-400);
  background: var(--ink-950);
  border: 1px solid var(--about-line);
}

.page-about .about-chapter__head {
  margin-bottom: 16px;
}

.page-about .about-chapter p {
  max-width: 38em;
  margin: 0 0 14px;
  line-height: 1.75;
}

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

.page-about .about-chapter a {
  color: var(--blue-300);
  text-decoration: none;
  border-bottom: 1px solid rgba(127, 180, 255, 0.4);
}

.page-about .about-chapter a:hover,
.page-about .about-chapter a:focus-visible {
  color: var(--cyan-500);
  border-bottom-color: var(--cyan-500);
}

/* ============ 图片容器 ============ */
.page-about .about-fig {
  margin: 20px 0;
}

.page-about .about-fig--2x1 {
  aspect-ratio: 2 / 1;
}

.page-about .about-fig--4x3 {
  aspect-ratio: 4 / 3;
}

.page-about .about-fig--10x7 {
  aspect-ratio: 10 / 7;
}

.page-about .img-frame img {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: cover;
}

/* ============ 版本刻度筛选 ============ */
.page-about .about-scale {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 1px;
  margin: 22px 0 4px;
  background: var(--about-line);
  border: 1px solid var(--about-line);
}

.page-about .about-scale__btn {
  border: 0;
  border-radius: 0;
  padding: 12px 6px;
  background: var(--ink-950);
  color: var(--slate-400);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
  cursor: pointer;
  transition: color 0.18s var(--ease), background-color 0.18s var(--ease);
}

.page-about .about-scale__btn:hover {
  color: var(--blue-300);
}

.page-about .about-scale__btn[aria-pressed="true"] {
  background: var(--cyan-500);
  color: var(--ink-950);
}

/* ============ 版本条目 ============ */
.page-about .about-versions {
  margin-top: 18px;
  border-top: 1px solid var(--about-line);
}

.page-about .about-version {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 4px;
  padding: 16px 0;
  border-bottom: 1px solid var(--about-line);
}

.page-about .about-version__no {
  font-size: 15px;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--cyan-500);
}

.page-about .about-version__title {
  margin: 0 0 6px;
  font-size: 17px;
  line-height: 1.5;
  color: var(--paper-050);
}

.page-about .about-version__title .stamp {
  margin-left: 8px;
  vertical-align: middle;
}

.page-about .about-version__text {
  margin: 0 0 10px;
  font-size: 15px;
  line-height: 1.7;
  color: var(--body-text);
}

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

.page-about .about-version--stable .about-version__no {
  color: var(--mint-400);
}

/* ============ 节点线路 ============ */
.page-about .about-nodegrid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 20px;
  margin-bottom: 22px;
}

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

.page-about .about-nodegrid__text p {
  max-width: 38em;
  margin: 0 0 14px;
  line-height: 1.75;
}

.page-about .about-nodegrid .about-fig {
  margin: 0;
}

.page-about .about-nodemap {
  margin: 4px 0 10px;
  padding: 10px;
  border: 1px solid var(--about-line);
  background:
    linear-gradient(rgba(23, 196, 214, 0.045) 1px, transparent 1px) 0 0 / 100% 48px,
    var(--ink-950);
}

.page-about .about-nodemap svg {
  display: block;
  width: 100%;
  height: auto;
}

.page-about .node-link {
  opacity: 1;
  pointer-events: bounding-box;
  transition: opacity 0.2s var(--ease);
}

.page-about .about-nodemap:hover .node-link {
  opacity: 0.22;
}

.page-about .about-nodemap .node-link:hover {
  opacity: 1;
}

.page-about .node-link line {
  stroke: var(--cyan-500);
  stroke-width: 1.4;
  stroke-opacity: 0.5;
  pointer-events: stroke;
}

.page-about .node-link circle {
  fill: var(--ink-950);
  stroke: var(--cyan-500);
  stroke-width: 1.6;
  pointer-events: all;
}

.page-about .node-hub circle {
  fill: var(--blue-600);
  stroke: var(--blue-300);
  stroke-width: 1.5;
}

/* ============ 维护节奏 ============ */
.page-about .about-rhythm {
  margin: 20px 0 0;
  padding: 0;
  list-style: none;
  border-top: 1px solid var(--about-line);
}

.page-about .about-rhythm__row {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 4px;
  padding: 18px 0;
  border-bottom: 1px solid var(--about-line);
}

.page-about .about-rhythm__cycle {
  font-size: 12px;
  letter-spacing: 0.12em;
  color: var(--amber-500);
}

.page-about .about-rhythm__title {
  margin: 0 0 6px;
  font-size: 17px;
  line-height: 1.5;
  color: var(--paper-050);
}

.page-about .about-rhythm__text {
  max-width: 38em;
  margin: 0;
  font-size: 15px;
  line-height: 1.7;
  color: var(--body-text);
}

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

/* ============ 三步指引 ============ */
.page-about .about-steps {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1px;
  margin: 20px 0 22px;
  padding: 0;
  list-style: none;
  background: var(--about-line);
  border: 1px solid var(--about-line);
}

.page-about .about-step {
  padding: 18px 18px 20px;
  background: var(--ink-950);
}

.page-about .about-step__no {
  display: block;
  margin-bottom: 8px;
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--cyan-500);
}

.page-about .about-step__title {
  margin: 0 0 8px;
  font-size: 17px;
  line-height: 1.5;
  color: var(--paper-050);
}

.page-about .about-step__text {
  margin: 0;
  font-size: 14.5px;
  line-height: 1.7;
  color: var(--body-text);
}

/* ============ 中等屏幕 ============ */
@media (min-width: 720px) {
  .page-about .about-hero {
    padding: 34px 0 48px;
  }

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

  .page-about .about-scale {
    grid-template-columns: repeat(5, minmax(0, 1fr));
  }

  .page-about .about-version,
  .page-about .about-rhythm__row {
    grid-template-columns: 116px minmax(0, 1fr);
    gap: 22px;
    align-items: start;
  }

  .page-about .about-version__no {
    padding-top: 1px;
  }

  .page-about .about-rhythm__cycle {
    padding-top: 4px;
  }

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

/* ============ 桌面：左刻度 + 右叙述 ============ */
@media (min-width: 900px) {
  .page-about .about-body {
    grid-template-columns: var(--about-axis-w) minmax(0, 1fr);
    gap: 52px;
    padding: 56px 0 96px;
  }

  .page-about .about-axis {
    position: sticky;
    top: 24px;
    display: block;
    align-self: start;
    padding: 0 0 0 18px;
    border-bottom: 0;
    border-left: 1px solid var(--about-line);
  }

  .page-about .about-axis__title {
    display: block;
    margin: 0 0 12px;
    font-size: 11px;
    letter-spacing: 0.14em;
    color: var(--slate-400);
  }

  .page-about .about-axis__item {
    position: relative;
    display: grid;
    grid-template-columns: auto minmax(0, 1fr);
    gap: 10px;
    padding: 9px 0;
    border: 0;
    background: none;
  }

  .page-about .about-axis__item::before {
    content: "";
    position: absolute;
    left: -19px;
    top: 50%;
    width: 10px;
    height: 1px;
    background: var(--about-line);
    transition: width 0.18s var(--ease), background-color 0.18s var(--ease);
  }

  .page-about .about-axis__item:hover::before {
    background: var(--blue-300);
  }

  .page-about .about-axis__item.is-current {
    border: 0;
    background: none;
    color: var(--cyan-500);
  }

  .page-about .about-axis__item.is-current::before {
    width: 16px;
    background: var(--cyan-500);
  }

  .page-about .about-nodegrid {
    grid-template-columns: minmax(0, 1fr) minmax(0, 380px);
    gap: 32px;
  }
}

@media (min-width: 1040px) {
  .page-about .about-chapter {
    padding: 34px 36px 40px;
  }

  .page-about .about-chapter:nth-child(2n) {
    margin-left: 16px;
  }

  .page-about .about-chapter__no {
    right: 26px;
  }
}

/* ============ 动效降级 ============ */
@media (prefers-reduced-motion: reduce) {
  .page-about .about-axis__item,
  .page-about .about-axis__item::before,
  .page-about .about-scale__btn,
  .page-about .node-link {
    transition-duration: 0.01ms;
  }
}