.page-about {
  --about-line-color: rgba(0, 212, 255, 0.25);
  --about-dot-size: 14px;
  --about-marker-width: 3rem;
  --about-gap: 1.25rem;
  --about-node-mb: 2.5rem;
  color: var(--text-primary);
  background: var(--bg-dark);
}

.page-about__container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 1.5rem 1rem 3rem;
}

/* ── 面包屑 ── */
.page-about__breadcrumb {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.8125rem;
  color: var(--text-secondary);
  margin-bottom: 2rem;
  letter-spacing: 0.02em;
}
.page-about__breadcrumb-link {
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--transition);
}
.page-about__breadcrumb-link:hover,
.page-about__breadcrumb-link:focus-visible {
  color: var(--primary);
}
.page-about__breadcrumb-sep {
  color: var(--text-secondary);
  opacity: 0.5;
}
.page-about__breadcrumb-current {
  color: var(--primary);
  font-weight: 600;
}

/* ── 标题区 ── */
.page-about__title {
  font-size: 2.25rem;
  font-weight: 800;
  letter-spacing: 0.06em;
  color: var(--text-primary);
  margin: 0 0 0.5rem;
  line-height: 1.1;
}
.page-about__subtitle {
  font-size: 1rem;
  color: var(--text-secondary);
  margin: 0 0 2.5rem;
  max-width: 40rem;
  line-height: 1.5;
}

/* ── 时间轴容器 ── */
.page-about__timeline {
  position: relative;
  padding-left: calc(var(--about-marker-width) + var(--about-gap));
}

/* 时间轴垂直线 */
.page-about__timeline::before {
  content: '';
  position: absolute;
  left: calc(var(--about-marker-width) / 2);
  top: 0;
  bottom: 0;
  width: 2px;
  background: linear-gradient(180deg, var(--primary) 0%, var(--secondary) 100%);
  opacity: 0.35;
  transform: translateX(-50%);
}

/* ── 节点 ── */
.page-about__node {
  position: relative;
  margin-bottom: var(--about-node-mb);
}
.page-about__node:last-child {
  margin-bottom: 0;
}

/* ── 标记（版本号 + 圆点） ── */
.page-about__node-marker {
  position: absolute;
  left: calc(-1 * (var(--about-marker-width) + var(--about-gap)));
  top: 0;
  width: var(--about-marker-width);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.375rem;
}

.page-about__version-link {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  font-weight: 700;
  color: var(--primary);
  text-decoration: none;
  letter-spacing: 0.04em;
  padding: 0.2rem 0.4rem;
  border: 1px solid transparent;
  transition: color var(--transition), border-color var(--transition), background var(--transition);
  border-radius: 2px;
  line-height: 1.2;
}
.page-about__version-link:hover,
.page-about__version-link:focus-visible {
  color: var(--accent-green);
  border-color: var(--accent-green);
  background: rgba(0, 255, 170, 0.08);
}

.page-about__node-dot {
  display: block;
  width: var(--about-dot-size);
  height: var(--about-dot-size);
  background: var(--secondary);
  border: 2px solid var(--bg-dark);
  border-radius: 50%;
  flex-shrink: 0;
  transition: transform var(--transition), box-shadow var(--transition);
  box-shadow: 0 0 0 2px var(--about-line-color);
}
.page-about__node-dot--highlight {
  background: var(--accent-green);
  box-shadow: 0 0 0 2px rgba(0, 255, 170, 0.3);
}

/* 节点悬停 —— 圆点反馈 */
.page-about__node:hover .page-about__node-dot,
.page-about__node:focus-within .page-about__node-dot {
  transform: scale(1.35);
  box-shadow: 0 0 0 4px rgba(255, 45, 85, 0.25), 0 0 1rem rgba(255, 45, 85, 0.15);
}
.page-about__node:hover .page-about__node-dot--highlight,
.page-about__node:focus-within .page-about__node-dot--highlight {
  box-shadow: 0 0 0 4px rgba(0, 255, 170, 0.25), 0 0 1rem rgba(0, 255, 170, 0.15);
}

/* ── 节点内容 ── */
.page-about__node-content {
  background: var(--bg-light);
  padding: 1.25rem 1.125rem;
  border-left: 3px solid var(--primary);
  transition: border-color var(--transition), background var(--transition);
  border-radius: 0;
}
.page-about__node:hover .page-about__node-content,
.page-about__node:focus-within .page-about__node-content {
  border-left-color: var(--secondary);
  background: rgba(26, 31, 38, 0.85);
}

.page-about__node-title {
  font-size: 1.375rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  color: var(--text-primary);
  margin: 0 0 0.75rem;
  line-height: 1.2;
}

.page-about__node-summary {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  margin: 0 0 1rem;
  line-height: 1.6;
  max-width: 48rem;
}

.page-about__node-detail {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.7;
  max-width: 48rem;
}
.page-about__node-detail p {
  margin: 0.75rem 0 0;
}
.page-about__node-detail p:first-child {
  margin-top: 0;
}

/* ── 节点图片 ── */
.page-about__node-img {
  display: block;
  max-width: 100%;
  height: auto;
  object-fit: cover;
  margin: 1rem 0 0.75rem;
  border: 1px solid rgba(255, 255, 255, 0.06);
  transition: border-color var(--transition);
}
.page-about__node-img--hero {
  margin-top: 1.25rem;
}
.page-about__node-img--small {
  max-width: 100%;
}
.page-about__node:hover .page-about__node-img {
  border-color: rgba(0, 212, 255, 0.2);
}
.page-about__node-caption {
  font-size: 0.75rem;
  color: var(--text-secondary);
  opacity: 0.7;
  margin: 0 0 0.25rem;
  letter-spacing: 0.03em;
}

/* ── 优势列表 ── */
.page-about__advantage-list {
  list-style: none;
  padding: 0;
  margin: 1rem 0 0;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}
.page-about__advantage-item {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  padding: 0.75rem 1rem;
  background: rgba(13, 17, 23, 0.5);
  border-left: 2px solid var(--primary);
  transition: border-color var(--transition), background var(--transition);
}
.page-about__advantage-item:hover {
  border-left-color: var(--secondary);
  background: rgba(13, 17, 23, 0.75);
}
.page-about__advantage-label {
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--primary);
  letter-spacing: 0.04em;
}
.page-about__advantage-desc {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* ── 底部链接导航 ── */
.page-about__links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem 1.5rem;
  margin-top: 3rem;
  padding-top: 2rem;
  border-top: 1px solid rgba(255, 255, 255, 0.06);
}
.page-about__link {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-secondary);
  text-decoration: none;
  letter-spacing: 0.03em;
  padding: 0.35rem 0;
  border-bottom: 2px solid transparent;
  transition: color var(--transition), border-color var(--transition);
}
.page-about__link:hover,
.page-about__link:focus-visible {
  color: var(--primary);
  border-bottom-color: var(--primary);
}

/* ========================================
   桌面增强
   ======================================== */
@media (min-width: 768px) {
  .page-about__container {
    padding: 2.5rem 2rem 4rem;
  }

  .page-about__breadcrumb {
    font-size: 0.875rem;
    margin-bottom: 2.5rem;
  }

  .page-about__title {
    font-size: 3.25rem;
  }
  .page-about__subtitle {
    font-size: 1.125rem;
    margin-bottom: 3.5rem;
  }

  .page-about {
    --about-marker-width: 4rem;
    --about-gap: 2rem;
    --about-dot-size: 16px;
    --about-node-mb: 3.5rem;
  }

  .page-about__node-content {
    padding: 1.75rem 2rem;
  }

  .page-about__node-title {
    font-size: 1.625rem;
  }
  .page-about__node-summary {
    font-size: 1rem;
  }
  .page-about__node-detail {
    font-size: 0.9375rem;
  }

  .page-about__version-link {
    font-size: 0.9375rem;
  }

  .page-about__node-img--small {
    max-width: 60%;
  }

  .page-about__advantage-item {
    flex-direction: row;
    align-items: baseline;
    gap: 1rem;
  }
  .page-about__advantage-label {
    flex: 0 0 8rem;
    font-size: 0.875rem;
  }
  .page-about__advantage-desc {
    font-size: 0.9375rem;
  }

  .page-about__links {
    gap: 1rem 2.5rem;
    margin-top: 4rem;
    padding-top: 2.5rem;
  }
  .page-about__link {
    font-size: 0.9375rem;
  }
}

@media (min-width: 1024px) {
  .page-about__container {
    padding: 3rem 2.5rem 5rem;
  }
  .page-about__title {
    font-size: 3.75rem;
  }
  .page-about__node-content {
    padding: 2rem 2.5rem;
  }
  .page-about__node-title {
    font-size: 1.75rem;
  }
}