/* =====================================================
   AI云学院 - 全局样式 V4 · 即构科技设计语言
   浅蓝白 × 亮蓝 × 蓝紫渐变 × 大圆角白卡 × 白色导航
   ===================================================== */
:root {
  /* 背景层：浅蓝白 */
  --bg: #f5f9ff;
  --bg-card: #ffffff;
  --bg-card-hover: #f0f6ff;
  --bg-soft: #eef4ff;
  /* 边框 */
  --border: #e2e8f0;
  --border-hover: rgba(22,119,255,.3);
  --border-soft: #eef2f7;
  /* 文字层：深色 */
  --text: #0f172a;
  --text-muted: #64748b;
  --text-soft: #94a3b8;
  /* 强调色：亮蓝 + 蓝紫渐变 */
  --accent: #1677ff;
  --accent-dark: #0958d9;
  --accent-glow: rgba(22,119,255,.1);
  --accent-2: #6366f1;
  --accent-3: #a855f7;
  --grad-brand: linear-gradient(120deg,#1677ff,#6366f1,#a855f7);
  --grad-soft: linear-gradient(135deg,rgba(22,119,255,.08),rgba(168,85,247,.08));
  /* 阴影：柔和 */
  --shadow: 0 2px 8px rgba(15,23,42,.04);
  --shadow-hover: 0 8px 28px rgba(15,23,42,.08);
  --shadow-blue: 0 8px 24px rgba(22,119,255,.18);
  /* 圆角：大圆角 */
  --radius: 16px;
  --radius-sm: 10px;
  --radius-tag: 24px;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "HarmonyOS Sans SC", "Microsoft YaHei", sans-serif;
  background: linear-gradient(180deg, #eaf2ff 0%, #f5f9ff 40%, #f5f9ff 100%);
  background-attachment: fixed;
  color: var(--text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; text-decoration: none; }
img { max-width: 100%; }

/* ============ 导航栏（首页 .site-nav） ============ */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: rgba(255,255,255,.94) !important;
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-soft);
  transition: box-shadow .3s;
}
.site-nav.scrolled {
  background: rgba(255,255,255,.97) !important;
  box-shadow: 0 4px 20px rgba(15,23,42,.06) !important;
}
.nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
  height: 66px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.nav-logo {
  font-size: 19px;
  font-weight: 800;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text);
}
.nav-logo img {
  width: 36px; height: 36px;
  border-radius: 50%;
  object-fit: cover;
  box-shadow: 0 4px 12px rgba(22,119,255,.2);
}
.nav-logo i { color: var(--accent); }
.nav-links {
  display: flex;
  gap: 2px;
  list-style: none;
  align-items: center;
}
.nav-links a {
  padding: 8px 15px;
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 500;
  color: var(--text-muted);
  transition: all .2s;
  cursor: pointer;
}
.nav-links a:hover { color: var(--accent); background: var(--accent-glow); }
.nav-links a.active { color: var(--accent); background: var(--accent-glow); font-weight: 600; }
.nav-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--text);
  font-size: 20px;
  cursor: pointer;
}

/* ============ 导航栏（内页 .navbar） ============ */
.navbar {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: rgba(255,255,255,.94);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-soft);
  transition: box-shadow .3s;
}
.navbar.scrolled {
  box-shadow: 0 4px 20px rgba(15,23,42,.06);
}
.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
  height: 66px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.navbar .logo {
  font-size: 19px;
  font-weight: 800;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text);
}
/* logo 图标自动替换为品牌图片 */
.navbar .logo i {
  display: inline-block;
  width: 36px;
  height: 36px;
  background: url(/assets/logo.png) no-repeat center center;
  background-size: cover;
  border-radius: 50%;
  box-shadow: 0 4px 12px rgba(22,119,255,.2);
  font-size: 0;
  flex-shrink: 0;
}
.navbar .logo i::before { display: none; }
.navbar .nav-links {
  display: flex;
  gap: 2px;
  list-style: none;
  align-items: center;
}
.navbar .nav-links a {
  padding: 8px 15px;
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 500;
  color: var(--text-muted);
  transition: all .2s;
  cursor: pointer;
}
.navbar .nav-links a:hover { color: var(--accent); background: var(--accent-glow); }
.navbar .nav-links a.active { color: var(--accent); background: var(--accent-glow); font-weight: 600; }
.navbar .nav-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--text);
  font-size: 20px;
  cursor: pointer;
}

/* ============ 搜索框 ============ */
.search-box {
  position: relative;
  margin-left: 16px;
}
.search-box input {
  width: 200px;
  padding: 8px 12px 8px 36px;
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-radius: var(--radius-tag);
  color: var(--text);
  font-size: 13px;
  outline: none;
  transition: all .2s;
}
.search-box input:focus {
  border-color: var(--accent);
  width: 260px;
  background: #fff;
  box-shadow: 0 0 0 3px var(--accent-glow);
}
.search-box i {
  position: absolute;
  left: 12px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-soft);
  font-size: 13px;
}

/* 搜索结果下拉 */
.search-results {
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  margin-top: 8px;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-hover);
  max-height: 400px;
  overflow-y: auto;
  display: none;
  z-index: 1001;
}
.search-results.show { display: block; }
.search-result-item {
  padding: 12px 16px;
  border-bottom: 1px solid var(--border-soft);
  cursor: pointer;
  transition: background .2s;
}
.search-result-item:hover { background: var(--bg-soft); }
.search-result-item:last-child { border-bottom: none; }
.search-result-title { font-size: 14px; font-weight: 600; margin-bottom: 4px; color: var(--text); }
.search-result-desc { font-size: 12px; color: var(--text-muted); }
.search-result-category {
  display: inline-block;
  font-size: 10px;
  padding: 2px 8px;
  border-radius: 4px;
  background: var(--accent-glow);
  color: var(--accent);
  margin-right: 8px;
  font-weight: 600;
}

/* ============ 面包屑 ============ */
.breadcrumb {
  max-width: 1200px;
  margin: 16px auto 0;
  padding: 0 24px;
  font-size: 13px;
  color: var(--text-muted);
}
.breadcrumb a { color: var(--text-muted); transition: color .2s; }
.breadcrumb a:hover { color: var(--accent); }
.breadcrumb span { margin: 0 8px; color: var(--text-soft); }
.breadcrumb .current { color: var(--text); font-weight: 500; }

/* ============ 阅读进度条 ============ */
.reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  background: var(--grad-brand);
  z-index: 999;
  width: 0;
  transition: width .1s;
}

/* ============ 回到顶部 ============ */
.back-to-top {
  position: fixed;
  bottom: 32px;
  right: 32px;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--accent);
  color: white;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 16px;
  box-shadow: var(--shadow-blue);
  opacity: 0;
  visibility: hidden;
  transform: translateY(20px);
  transition: all .3s ease;
  z-index: 998;
}
.back-to-top.show {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.back-to-top:hover { transform: translateY(-4px); box-shadow: 0 12px 28px rgba(22,119,255,.35); }

/* ============ 容器 ============ */
.container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }

/* ============ 页面标题区 ============ */
.page-header {
  padding: 56px 0 36px;
  text-align: center;
}
.page-header .badge {
  display: inline-block;
  padding: 7px 18px;
  background: var(--accent-glow);
  color: var(--accent);
  border-radius: var(--radius-tag);
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 16px;
}
.page-header h1 {
  font-size: 36px;
  font-weight: 800;
  margin-bottom: 12px;
  color: var(--text);
  letter-spacing: -.3px;
}
.page-header h1 .accent {
  background: var(--grad-brand);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}
.page-header p {
  font-size: 15px;
  color: var(--text-muted);
  max-width: 600px;
  margin: 0 auto;
  line-height: 1.8;
}

/* ============ 卡片通用 ============ */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border-soft);
  border-radius: var(--radius);
  padding: 24px;
  transition: all .3s ease;
  box-shadow: var(--shadow);
}
.card:hover {
  border-color: var(--border-hover);
  transform: translateY(-4px);
  box-shadow: var(--shadow-hover);
}

/* ============ 网格 ============ */
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; }

/* ============ 按钮 ============ */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 22px;
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: all .25s;
}
.btn-primary {
  background: var(--accent);
  color: white;
  box-shadow: var(--shadow-blue);
}
.btn-primary:hover {
  background: var(--accent-dark);
  transform: translateY(-2px);
  box-shadow: 0 12px 28px rgba(22,119,255,.3);
}
.btn-secondary {
  background: #fff;
  color: var(--text);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
}
.btn-secondary:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-2px);
}

/* ============ 标签 ============ */
.tag {
  display: inline-block;
  padding: 4px 12px;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 12px;
  color: var(--text-muted);
  margin: 2px;
  cursor: pointer;
  transition: all .2s;
}
.tag:hover, .tag.active {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-glow);
}

/* ============ 页脚 ============ */
.site-footer {
  margin-top: 80px;
  padding: 56px 0 28px;
  background: #fff;
  border-top: 1px solid var(--border-soft);
}
.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  margin-bottom: 32px;
}
.footer-brand .logo {
  font-size: 19px;
  font-weight: 800;
  margin-bottom: 14px;
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text);
}
.footer-brand .logo img {
  width: 32px; height: 32px;
  border-radius: 50%;
  object-fit: cover;
}
.footer-brand .logo i { color: var(--accent); }
.footer-brand p { font-size: 13px; color: var(--text-muted); line-height: 1.9; }
.footer-col h4 { font-size: 14px; font-weight: 700; margin-bottom: 16px; color: var(--text); }
.footer-col a {
  display: block;
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 10px;
  transition: color .2s;
  cursor: pointer;
}
.footer-col a:hover { color: var(--accent); }
.footer-bottom {
  text-align: center;
  padding-top: 24px;
  border-top: 1px solid var(--border-soft);
  font-size: 13px;
  color: var(--text-soft);
}

/* ============ 404页面 ============ */
.error-page {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 40px;
}
.error-code {
  font-size: 120px;
  font-weight: 800;
  background: var(--grad-brand);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  line-height: 1;
  margin-bottom: 16px;
}
.error-title { font-size: 28px; margin-bottom: 12px; color: var(--text); }
.error-desc { font-size: 16px; color: var(--text-muted); margin-bottom: 32px; }
.error-actions { display: flex; gap: 16px; justify-content: center; }

/* ============ 渐入动画 ============ */
.reveal {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity .7s cubic-bezier(.16,1,.3,1), transform .7s cubic-bezier(.16,1,.3,1);
}
.reveal.visible { opacity: 1; transform: translateY(0); }
.reveal-delay-1 { transition-delay: .1s; }
.reveal-delay-2 { transition-delay: .2s; }
.reveal-delay-3 { transition-delay: .3s; }

/* ============ 响应式 ============ */
@media (max-width: 900px) {
  .navbar .nav-toggle, .site-nav .nav-toggle { display: block; }
  .navbar .nav-links, .site-nav .nav-links {
    display: none;
    position: absolute;
    top: 66px;
    left: 0;
    right: 0;
    background: #fff;
    flex-direction: column;
    padding: 12px;
    border-bottom: 1px solid var(--border-soft);
    box-shadow: 0 8px 24px rgba(15,23,42,.08);
  }
  .navbar .nav-links.open, .site-nav .nav-links.open { display: flex; }
  .navbar .nav-links a, .site-nav .nav-links a { width: 100%; padding: 12px 16px; }
  .search-box { display: none; }
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .page-header h1 { font-size: 28px; }
  .back-to-top { bottom: 20px; right: 20px; width: 40px; height: 40px; }
}

@media (prefers-reduced-motion: reduce) {
  .reveal { opacity: 1; transform: none; transition: none; }
  html { scroll-behavior: auto; }
}