.page-about {
  --page-bg: var(--color-bg);
  --page-card-bg: var(--color-surface);
  --page-accent: var(--color-accent);
  --page-accent-secondary: var(--color-accent-secondary);
  --page-accent-highlight: var(--color-accent-highlight);
  --page-text: var(--color-text);
  --page-text-secondary: var(--color-text-secondary);
  --page-glow: 0 0 12px rgba(26, 92, 255, 0.4), 0 0 30px rgba(26, 92, 255, 0.15);
  --page-timeline-width: 3px;
  --page-node-size: 14px;
  --page-sidebar-width: 200px;
  --page-chapter-gap: 3rem;
  background: var(--page-bg);
  color: var(--page-text);
  font-family: var(--font-body);
  padding-bottom: var(--space-xl);
  overflow-x: hidden;
}

/* ── Hero ── */
.page-about__hero {
  padding: var(--space-lg) var(--space-sm) var(--space-md);
  position: relative;
  z-index: 1;
}
.page-about__hero::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--page-accent), var(--page-accent-secondary), transparent);
}
.page-about__breadcrumb {
  font-size: 0.85rem;
  font-family: var(--font-heading);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--page-text-secondary);
  margin-bottom: var(--space-sm);
}
.page-about__breadcrumb-link {
  color: var(--page-accent);
  text-decoration: none;
  transition: color 0.3s;
}
.page-about__breadcrumb-link:hover,
.page-about__breadcrumb-link:focus-visible {
  color: var(--page-accent-highlight);
  outline: none;
}
.page-about__breadcrumb-sep {
  margin: 0 0.4em;
  color: var(--page-text-secondary);
}
.page-about__breadcrumb-current {
  color: var(--page-text);
}
.page-about__title {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: clamp(2.2rem, 6vw, 3.8rem);
  line-height: 1.1;
  margin: 0 0 var(--space-xs);
  text-shadow: var(--page-glow);
  letter-spacing: -0.02em;
}
.page-about__subtitle {
  font-family: var(--font-heading);
  font-weight: 500;
  font-size: clamp(0.9rem, 2vw, 1.2rem);
  color: var(--page-text-secondary);
  margin: 0;
  letter-spacing: 0.03em;
}

/* ── Body — 移动端单栏 ── */
.page-about__body {
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
  margin-top: var(--space-md);
  padding: 0 var(--space-sm);
}

/* ── Sidebar / TOC ── */
.page-about__sidebar {
  order: 0;
  flex-shrink: 0;
}
.page-about__toc {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-wrap: nowrap;
  gap: var(--space-xs);
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
}
.page-about__toc::-webkit-scrollbar {
  display: none;
}
.page-about__toc-item {
  flex: 0 0 auto;
}
.page-about__toc-link {
  display: block;
  padding: 0.5em 1.2em;
  font-family: var(--font-heading);
  font-weight: 500;
  font-size: 0.85rem;
  color: var(--page-text-secondary);
  text-decoration: none;
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 2em;
  background: var(--glass);
  white-space: nowrap;
  transition: all 0.3s ease;
}
.page-about__toc-link:hover,
.page-about__toc-link:focus-visible {
  color: var(--page-text);
  border-color: var(--page-accent);
  background: rgba(26, 92, 255, 0.1);
  outline: none;
  box-shadow: 0 0 12px rgba(26, 92, 255, 0.2);
}

/* ── Chapters 容器 ── */
.page-about__chapters {
  order: 1;
  position: relative;
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: var(--page-chapter-gap);
}
/* 时间线 — 贯穿所有章节的垂直线 */
.page-about__chapters::before {
  content: '';
  position: absolute;
  top: 0;
  bottom: 0;
  left: 16px;
  width: var(--page-timeline-width);
  background: linear-gradient(180deg, var(--page-accent), var(--page-accent-secondary), transparent 90%);
  border-radius: 2px;
  z-index: 0;
  pointer-events: none;
}

/* ── 单个章节卡片 ── */
.page-about__chapter {
  position: relative;
  z-index: 1;
  padding-left: 44px;
  scroll-margin-top: calc(var(--nav-height, 64px) + 20px);
}
/* 时间线节点 — 每个章节对应一个圆点 */
.page-about__chapter::before {
  content: '';
  position: absolute;
  left: 10px;
  top: 32px;
  width: var(--page-node-size);
  height: var(--page-node-size);
  border-radius: 50%;
  background: var(--page-accent);
  box-shadow: 0 0 0 3px var(--page-bg), 0 0 0 5px var(--page-accent), var(--page-glow);
  z-index: 2;
  pointer-events: none;
}
/* 章节内部容器 — 纸张叠层效果 */
.page-about__chapter-inner {
  background: var(--page-card-bg);
  border-radius: var(--radius);
  padding: var(--space-md) var(--space-sm);
  position: relative;
  box-shadow:
    0 1px 3px rgba(0,0,0,0.45),
    0 4px 12px rgba(0,0,0,0.35),
    0 8px 24px rgba(0,0,0,0.25),
    0 16px 48px rgba(0,0,0,0.1);
  border: 1px solid rgba(255, 255, 255, 0.04);
  transition: box-shadow 0.4s, border-color 0.4s;
}
/* 斜切装饰条 — 章节顶部 */
.page-about__chapter-inner::before {
  content: '';
  position: absolute;
  top: -1px;
  left: 0;
  right: 0;
  height: 6px;
  background: linear-gradient(90deg, var(--page-accent), var(--page-accent-secondary));
  clip-path: polygon(0 0, 100% 0, 100% 100%, 0 100%);
  transform: skewY(-0.8deg);
  transform-origin: left top;
  border-radius: var(--radius) var(--radius) 0 0;
  z-index: 3;
}
/* 章节编号 */
.page-about__chapter-number {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.75rem;
  color: var(--page-accent);
  letter-spacing: 0.15em;
  display: inline-block;
  margin-bottom: 0.25rem;
  text-transform: uppercase;
  opacity: 0.8;
}
/* 章节标题 */
.page-about__chapter-title {
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: clamp(1.4rem, 3vw, 2rem);
  margin: 0 0 var(--space-sm);
  color: var(--page-text);
  line-height: 1.2;
}
/* 内容布局 — 移动端文字在上，图片在下 */
.page-about__chapter-content {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}
.page-about__chapter-text {
  font-size: 1rem;
  line-height: 1.7;
  color: var(--page-text-secondary);
}
.page-about__chapter-text p {
  margin: 0 0 var(--space-sm);
}
.page-about__chapter-text p:last-of-type {
  margin-bottom: var(--space-xs);
}
.page-about__cta-link {
  display: inline-block;
  font-family: var(--font-heading);
  font-weight: 500;
  font-size: 0.95rem;
  color: var(--page-accent);
  text-decoration: none;
  padding: 0.3em 0;
  border-bottom: 1px solid transparent;
  transition: all 0.3s ease;
}
.page-about__cta-link:hover,
.page-about__cta-link:focus-visible {
  color: var(--page-accent-highlight);
  border-bottom-color: var(--page-accent-highlight);
  outline: none;
  text-shadow: 0 0 8px rgba(57, 255, 20, 0.3);
}
/* 图片 */
.page-about__chapter-image {
  width: 100%;
  border-radius: calc(var(--radius) + 2px);
  overflow: hidden;
  background: var(--page-bg);
  order: 1;
}
.page-about__img {
  display: block;
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  aspect-ratio: 800 / 600;
  border-radius: inherit;
  transition: transform 0.5s ease, box-shadow 0.5s ease;
}
.page-about__chapter-image:hover .page-about__img,
.page-about__chapter-image:focus-within .page-about__img {
  transform: scale(1.02);
  box-shadow: 0 0 30px rgba(26, 92, 255, 0.15);
}

/* ── :target 高亮当前章节 ── */
.page-about__chapter:target .page-about__chapter-inner {
  border-color: var(--page-accent);
  box-shadow:
    0 1px 3px rgba(0,0,0,0.45),
    0 4px 12px rgba(0,0,0,0.35),
    0 0 0 1px var(--page-accent),
    0 16px 48px rgba(0,0,0,0.1);
}
.page-about__chapter:target .page-about__chapter-title {
  text-shadow: var(--page-glow);
}
.page-about__chapter:target::before {
  background: var(--page-accent-highlight);
  box-shadow: 0 0 0 3px var(--page-bg), 0 0 0 5px var(--page-accent-highlight), 0 0 20px var(--page-accent-highlight);
}

/* ── 桌面端 ≥768px ── */
@media (min-width: 768px) {
  .page-about__hero {
    padding: var(--space-xl) var(--space-md) var(--space-lg);
  }
  .page-about__body {
    flex-direction: row;
    gap: var(--space-xl);
    margin-top: var(--space-lg);
    padding: 0 var(--space-md);
  }
  /* 侧边目录 — 固定定位 */
  .page-about__sidebar {
    order: 0;
    width: var(--page-sidebar-width);
    position: sticky;
    top: calc(var(--nav-height, 64px) + var(--space-md));
    align-self: flex-start;
    flex-shrink: 0;
  }
  .page-about__toc {
    flex-direction: column;
    gap: var(--space-xs);
    overflow: visible;
    padding: var(--space-sm) 0;
    border-left: 2px solid rgba(255, 255, 255, 0.06);
    padding-left: var(--space-sm);
  }
  .page-about__toc-link {
    border: none;
    border-radius: 0;
    background: transparent;
    padding: 0.4em 0;
    font-size: 0.9rem;
    white-space: normal;
    position: relative;
    transition: color 0.3s, padding-left 0.3s;
  }
  .page-about__toc-link::before {
    content: '';
    position: absolute;
    left: calc(-1 * var(--space-sm) - 2px);
    top: 50%;
    transform: translateY(-50%);
    width: 4px;
    height: 0;
    background: var(--page-accent);
    border-radius: 2px;
    transition: height 0.3s;
  }
  .page-about__toc-link:hover,
  .page-about__toc-link:focus-visible {
    color: var(--page-accent);
    background: transparent;
    padding-left: 0.3em;
    box-shadow: none;
  }
  .page-about__toc-link:hover::before,
  .page-about__toc-link:focus-visible::before {
    height: 60%;
  }
  /* 目录链接对应 :target 高亮 — 利用 :has() 进阶增强 */
  .page-about__toc-item:has(.page-about__toc-link[href="#mission"]:focus) ~ .page-about__chapters #mission .page-about__chapter-inner,
  .page-about__toc-item:has(.page-about__toc-link[href="#scope"]:focus) ~ .page-about__chapters #scope .page-about__chapter-inner,
  .page-about__toc-item:has(.page-about__toc-link[href="#commitment"]:focus) ~ .page-about__chapters #commitment .page-about__chapter-inner {
    border-color: var(--page-accent-secondary);
  }

  /* 章节内容 — 桌面端图文并排 */
  .page-about__chapters {
    gap: 4rem;
  }
  .page-about__chapters::before {
    left: -24px;
  }
  .page-about__chapter {
    padding-left: 0;
  }
  .page-about__chapter::before {
    left: -30px;
    top: 40px;
  }
  .page-about__chapter-inner {
    padding: var(--space-lg) var(--space-md);
  }
  .page-about__chapter-inner::before {
    height: 8px;
    transform: skewY(-0.6deg);
  }
  .page-about__chapter-content {
    flex-direction: row;
    align-items: flex-start;
    gap: var(--space-lg);
  }
  .page-about__chapter-text {
    flex: 1 1 55%;
  }
  .page-about__chapter-image {
    flex: 1 1 40%;
    order: 0;
    margin-top: 0;
  }
  .page-about__chapter-image:last-child {
    margin-left: auto;
  }
  /* 交替图片左右 */
  .page-about__chapter:nth-child(even) .page-about__chapter-content {
    flex-direction: row-reverse;
  }
  .page-about__chapter:nth-child(even) .page-about__chapter-image {
    margin-left: 0;
    margin-right: auto;
  }
}

/* ── 大桌面 ≥1024px ── */
@media (min-width: 1024px) {
  .page-about__hero {
    padding: var(--space-xl) 0 var(--space-lg);
  }
  .page-about__body {
    padding: 0;
    gap: 5rem;
  }
  .page-about__sidebar {
    width: 220px;
  }
  .page-about__chapter-inner {
    padding: var(--space-xl) var(--space-lg);
  }
  .page-about__chapter-content {
    gap: var(--space-xl);
  }
  .page-about__chapter-text {
    font-size: 1.05rem;
  }
}

/* ── 防止溢出 ── */
.container {
  max-width: var(--max-width, 1280px);
  margin-left: auto;
  margin-right: auto;
  width: 100%;
}
.img-container {
  line-height: 0;
  display: block;
}
.img-container img {
  max-width: 100%;
  height: auto;
  display: block;
}

/* ── 共享 glow-text 在此作用域强化 ── */
.glow-text {
  text-shadow: var(--page-glow);
}