/* page-about 专属 CSS */
.page-about {
  --page-accent: #FF6600;
  --page-primary: #0055A4;
  --page-bg: #F5F5F5;
  --page-text: #2C2C2C;
  --page-mono: 'JetBrains Mono', monospace;
  --page-sans: 'Inter', 'Noto Sans SC', sans-serif;
  --page-header-height: 70px;
  --page-nav-width: 220px;
  --page-content-max: 720px;
}

/* 目录式索引布局：左侧导航 + 右侧内容 */
.page-about__wrapper {
  display: flex;
  gap: 2rem;
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem 1rem;
  min-height: 70vh;
}

/* 左侧导航 */
.page-about__nav {
  flex: 0 0 var(--page-nav-width);
  position: sticky;
  top: calc(var(--page-header-height) + 1rem);
  align-self: flex-start;
  max-height: calc(100vh - var(--page-header-height) - 3rem);
  overflow-y: auto;
  border-right: 1px solid rgba(0,85,164,0.2);
  padding-right: 1rem;
}

.page-about__nav-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.page-about__nav-link {
  display: block;
  padding: 0.6em 0;
  font-family: var(--page-mono);
  font-size: 0.9rem;
  text-decoration: none;
  color: #666;
  transition: color 0.2s, font-weight 0.2s;
  border-left: 3px solid transparent;
  padding-left: 0.8rem;
}

.page-about__nav-link:hover,
.page-about__nav-link:focus {
  color: var(--page-accent);
}

/* 高亮状态由JS驱动，但CSS定义样式 */
.page-about__nav-link.active {
  color: var(--page-primary);
  font-weight: 700;
  border-left-color: var(--page-accent);
}

/* 右侧内容区 */
.page-about__content {
  flex: 1;
  max-width: var(--page-content-max);
}

/* 隐藏h1 */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0,0,0,0);
  border: 0;
}

/* 面包屑 */
.breadcrumb {
  font-family: var(--page-mono);
  font-size: 0.85rem;
  color: #888;
  margin-bottom: 1.5rem;
}

.breadcrumb__link {
  color: var(--page-primary);
  text-decoration: none;
}

.breadcrumb__link:hover {
  text-decoration: underline;
}

.breadcrumb__separator {
  margin: 0 0.4em;
  color: #ccc;
}

.breadcrumb__current {
  color: var(--page-text);
}

/* 首屏背景 */
.page-about__hero {
  position: relative;
  width: 100%;
  height: 300px;
  overflow: hidden;
  margin-bottom: 2rem;
  border-bottom: 3px solid var(--page-accent);
}

.page-about__hero-image {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

.page-about__hero-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(0,85,164,0.6) 0%, transparent 100%);
  pointer-events: none;
}

/* 引言 */
.page-about__intro-text {
  font-size: 1.1rem;
  line-height: 1.7;
  color: #444;
  padding: 1.5rem 0;
  border-bottom: 2px solid rgba(0,85,164,0.15);
  margin-bottom: 2rem;
}

/* 章节 */
.page-about__section {
  margin-bottom: 3.5rem;
  scroll-margin-top: calc(var(--page-header-height) + 2rem);
}

.page-about__section-header {
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  margin-bottom: 1.2rem;
}

.page-about__section-number {
  font-family: var(--page-mono);
  font-size: 2rem;
  font-weight: 700;
  color: var(--page-accent);
  line-height: 1;
  opacity: 0.7;
}

.page-about__section-title {
  font-family: var(--page-sans);
  font-size: 1.8rem;
  font-weight: 700;
  font-style: italic;
  color: var(--page-primary);
  margin: 0;
  letter-spacing: -0.02em;
}

.page-about__section-body {
  font-size: 1rem;
  line-height: 1.7;
  color: var(--page-text);
}

.page-about__section-body p {
  margin-bottom: 1em;
}

/* 服务特色网格 */
.page-about__features-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
}

.page-about__feature-item {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  padding: 1rem 0;
  border-bottom: 1px dashed rgba(0,85,164,0.2);
}

.page-about__feature-image {
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: contain;
  border-radius: 0;
  border: 1px solid rgba(0,0,0,0.05);
}

.page-about__feature-heading {
  font-family: var(--page-sans);
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--page-primary-dark, #003D7A);
  margin: 0 0 0.3rem 0;
}

.page-about__feature-text p {
  margin: 0;
  color: #555;
}

/* 版本演进 */
.page-about__evolution-wrapper {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.page-about__evolution-image {
  width: 100%;
  max-width: 100%;
  height: auto;
  object-fit: contain;
  border: 1px solid rgba(0,0,0,0.06);
}

.page-about__evolution-text p {
  margin-bottom: 1em;
}

/* 可展开 */
.page-about__details {
  margin-top: 1.5rem;
  border: 1px solid rgba(0,85,164,0.2);
  border-radius: 0;
}

.page-about__details-summary {
  cursor: pointer;
  padding: 0.75rem 1rem;
  font-family: var(--page-mono);
  font-size: 0.9rem;
  color: var(--page-primary);
  background: rgba(0,85,164,0.04);
  transition: background 0.2s;
  list-style: none;
}

.page-about__details-summary::-webkit-details-marker {
  display: none;
}

.page-about__details-summary:hover {
  background: rgba(0,85,164,0.1);
}

.page-about__details-content {
  padding: 1rem;
  border-top: 1px solid rgba(0,85,164,0.1);
}

.page-about__details-content p {
  margin-bottom: 0.75em;
}

/* 联系方式 */
.page-about__contact-info {
  background: var(--page-bg);
  padding: 1.2rem;
  border-left: 4px solid var(--page-accent);
  font-size: 0.95rem;
  line-height: 1.8;
}

.page-about__contact-info .note {
  font-size: 0.85rem;
  color: #888;
  font-style: italic;
}

/* 页内链接 */
.page-about__internal-links {
  display: flex;
  gap: 1.5rem;
  padding-top: 2rem;
  border-top: 2px solid rgba(0,85,164,0.15);
  margin-top: 1rem;
}

.page-about__link {
  font-family: var(--page-mono);
  font-size: 0.9rem;
  color: var(--page-primary);
  text-decoration: none;
  transition: color 0.2s;
}

.page-about__link:hover {
  color: var(--page-accent);
  text-decoration: underline;
}

/* 移动端优先 */
@media (max-width: 768px) {
  .page-about__wrapper {
    flex-direction: column;
    padding: 1rem 0.75rem;
  }

  .page-about__nav {
    flex: none;
    position: static;
    width: 100%;
    border-right: none;
    border-bottom: 1px solid rgba(0,85,164,0.15);
    padding: 0 0 0.75rem 0;
    overflow: visible;
    max-height: none;
  }

  .page-about__nav-list {
    display: flex;
    flex-wrap: wrap;
    gap: 0.3rem;
  }

  .page-about__nav-link {
    padding: 0.4em 0.8em;
    border-left: none;
    border-bottom: 3px solid transparent;
    font-size: 0.8rem;
  }

  .page-about__nav-link.active {
    border-left: none;
    border-bottom-color: var(--page-accent);
  }

  .page-about__content {
    max-width: 100%;
  }

  .page-about__hero {
    height: 200px;
  }

  .page-about__section-title {
    font-size: 1.4rem;
  }

  .page-about__section-number {
    font-size: 1.5rem;
  }

  .page-about__features-grid {
    gap: 1.2rem;
  }

  .page-about__internal-links {
    flex-direction: column;
    gap: 0.8rem;
  }

  .page-about__contact-info {
    font-size: 0.9rem;
  }
}

@media (min-width: 769px) {
  .page-about__features-grid {
    grid-template-columns: 1fr;
  }

  .page-about__feature-item {
    flex-direction: row;
    align-items: flex-start;
  }

  .page-about__feature-image {
    max-width: 280px;
    flex-shrink: 0;
  }

  .page-about__evolution-wrapper {
    flex-direction: row;
    align-items: flex-start;
  }

  .page-about__evolution-image {
    max-width: 300px;
    flex-shrink: 0;
  }
}

.page-about {
  --page-primary-dark: var(--color-primary-dark);
}