/* ================= 主题变量 ================= */
:root {
  --color-primary: #1E5BB8;
  --color-primary-dark: #154790;
  --color-primary-light: #4F86D1;
  --color-accent: #2C7BE5;
  --color-bg: #F5F7FA;
  --color-bg-alt: #FFFFFF;
  --color-border: #E3E8EF;
  --color-text: #2C3E50;
  --color-text-soft: #5A6B7D;
  --color-text-muted: #8492A6;
  --color-success: #1F9D55;
  --color-warning: #E0A800;
  --shadow-sm: 0 1px 3px rgba(28, 49, 88, 0.06);
  --shadow-md: 0 4px 12px rgba(28, 49, 88, 0.08);
  --shadow-lg: 0 8px 24px rgba(28, 49, 88, 0.10);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
}

/* ================= 基础重置 ================= */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html, body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
               "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  font-size: 15px;
  line-height: 1.7;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color .15s ease;
}
a:hover { color: var(--color-primary-dark); }

ul, ol { padding-left: 1.2em; }
li { margin: 4px 0; }

img { max-width: 100%; display: block; }

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

/* ================= 导航栏 ================= */
.site-header {
  background: #FFFFFF;
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow-sm);
}
.nav-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}
.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--color-text);
}
.logo-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  background: var(--color-primary);
  color: #FFFFFF;
  font-weight: 700;
  font-size: 18px;
  border-radius: var(--radius-sm);
}
.logo-text {
  font-size: 18px;
  font-weight: 700;
  color: var(--color-primary);
}
.logo-sub {
  font-size: 12px;
  color: var(--color-text-muted);
  padding-left: 6px;
  border-left: 1px solid var(--color-border);
  margin-left: 4px;
}
.main-nav {
  display: flex;
  align-items: center;
  gap: 8px;
}
.nav-link {
  display: inline-block;
  padding: 8px 18px;
  font-size: 15px;
  font-weight: 500;
  color: var(--color-text-soft);
  border-radius: var(--radius-sm);
  transition: all .15s ease;
}
.nav-link:hover {
  color: var(--color-primary);
  background: rgba(30, 91, 184, 0.06);
}
.nav-link.active {
  color: #FFFFFF;
  background: var(--color-primary);
}
.nav-link.active:hover {
  color: #FFFFFF;
  background: var(--color-primary-dark);
}

/* ================= 主体区域 ================= */
.site-main {
  min-height: calc(100vh - 64px - 180px);
  padding: 32px 0 64px;
}

/* ================= 页脚 ================= */
.site-footer {
  background: #FFFFFF;
  border-top: 1px solid var(--color-border);
  color: var(--color-text-soft);
  margin-top: 48px;
}
.footer-container {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1.2fr;
  gap: 48px;
  padding: 40px 24px 24px;
}
.footer-logo {
  font-size: 18px;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 8px;
}
.footer-desc { color: var(--color-text-muted); font-size: 13px; }
.footer-title {
  font-size: 14px;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 10px;
}
.footer-link, .footer-text {
  display: block;
  color: var(--color-text-soft);
  font-size: 13px;
  margin: 4px 0;
}
.footer-link:hover { color: var(--color-primary); }
.footer-bottom {
  border-top: 1px solid var(--color-border);
  padding: 16px 0;
  text-align: center;
  font-size: 12px;
  color: var(--color-text-muted);
}

/* ================= Banner ================= */
.banner {
  background: linear-gradient(135deg, #1E5BB8 0%, #2C7BE5 100%);
  color: #FFFFFF;
  border-radius: var(--radius-lg);
  padding: 64px 56px;
  margin-bottom: 40px;
  box-shadow: var(--shadow-md);
  position: relative;
  overflow: hidden;
}
.banner::after {
  content: "";
  position: absolute;
  right: -80px;
  top: -80px;
  width: 320px;
  height: 320px;
  background: rgba(255, 255, 255, 0.08);
  border-radius: 50%;
}
.banner::before {
  content: "";
  position: absolute;
  right: 80px;
  bottom: -120px;
  width: 200px;
  height: 200px;
  background: rgba(255, 255, 255, 0.06);
  border-radius: 50%;
}
.banner-eyebrow {
  display: inline-block;
  background: rgba(255, 255, 255, 0.18);
  color: #FFFFFF;
  font-size: 12px;
  font-weight: 500;
  padding: 4px 12px;
  border-radius: 999px;
  margin-bottom: 16px;
  letter-spacing: 1px;
}
.banner-title {
  font-size: 36px;
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: 16px;
  position: relative;
  z-index: 1;
}
.banner-subtitle {
  font-size: 16px;
  line-height: 1.7;
  max-width: 680px;
  opacity: .92;
  margin-bottom: 28px;
  position: relative;
  z-index: 1;
}
.banner-actions {
  display: flex;
  gap: 12px;
  position: relative;
  z-index: 1;
}

/* ================= 按钮 ================= */
.btn {
  display: inline-block;
  padding: 10px 22px;
  font-size: 14px;
  font-weight: 500;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  cursor: pointer;
  transition: all .15s ease;
  text-align: center;
}
.btn-primary {
  background: #FFFFFF;
  color: var(--color-primary);
  border-color: #FFFFFF;
}
.btn-primary:hover {
  background: #F0F4FA;
  color: var(--color-primary-dark);
}
.btn-outline {
  background: transparent;
  color: #FFFFFF;
  border-color: rgba(255, 255, 255, 0.6);
}
.btn-outline:hover {
  background: rgba(255, 255, 255, 0.12);
  color: #FFFFFF;
}
.btn-solid {
  background: var(--color-primary);
  color: #FFFFFF;
}
.btn-solid:hover {
  background: var(--color-primary-dark);
  color: #FFFFFF;
}

/* ================= 区块标题 ================= */
.section {
  margin: 48px 0;
}
.section-header {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  margin-bottom: 24px;
  border-bottom: 1px solid var(--color-border);
  padding-bottom: 14px;
}
.section-title {
  font-size: 22px;
  font-weight: 700;
  color: var(--color-text);
}
.section-subtitle {
  font-size: 13px;
  color: var(--color-text-muted);
  margin-top: 4px;
}
.section-more {
  font-size: 14px;
  color: var(--color-primary);
}

/* ================= 卡片网格 ================= */
.card-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}
@media (max-width: 900px) {
  .card-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 600px) {
  .card-grid { grid-template-columns: 1fr; }
}

.card {
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 24px;
  transition: all .2s ease;
  display: flex;
  flex-direction: column;
  height: 100%;
}
.card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--color-primary-light);
}
.card-tag {
  display: inline-block;
  font-size: 12px;
  color: var(--color-primary);
  background: rgba(30, 91, 184, 0.10);
  padding: 3px 10px;
  border-radius: 999px;
  margin-bottom: 12px;
  font-weight: 500;
}
.card-title {
  font-size: 17px;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 8px;
  line-height: 1.4;
}
.card-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  font-size: 12px;
  color: var(--color-text-muted);
  margin-bottom: 12px;
}
.card-meta span::before {
  content: "·";
  margin-right: 8px;
  color: var(--color-border);
}
.card-meta span:first-child::before { content: ""; margin-right: 0; }
.card-summary {
  font-size: 13.5px;
  color: var(--color-text-soft);
  line-height: 1.6;
  margin-bottom: 18px;
  flex: 1;
}
.card-link {
  font-size: 13px;
  font-weight: 500;
  color: var(--color-primary);
  align-self: flex-start;
}
.card-link::after {
  content: " →";
  transition: margin-left .15s ease;
}
.card-link:hover::after { margin-left: 4px; }

/* ================= 数据展示区 ================= */
.stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
  margin: 48px 0;
}
@media (max-width: 700px) {
  .stats { grid-template-columns: repeat(2, 1fr); }
}
.stat-card {
  background: #FFFFFF;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 24px 20px;
  text-align: center;
  transition: all .2s ease;
}
.stat-card:hover {
  border-color: var(--color-primary-light);
  box-shadow: var(--shadow-sm);
}
.stat-value {
  font-size: 32px;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 6px;
  line-height: 1.1;
}
.stat-label {
  font-size: 13px;
  color: var(--color-text-soft);
}

/* ================= 页面标题 ================= */
.page-header {
  background: #FFFFFF;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 32px 36px;
  margin-bottom: 32px;
  box-shadow: var(--shadow-sm);
}
.page-eyebrow {
  font-size: 12px;
  color: var(--color-primary);
  letter-spacing: 1.5px;
  font-weight: 600;
  margin-bottom: 8px;
}
.page-title {
  font-size: 28px;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 8px;
}
.page-desc {
  color: var(--color-text-soft);
  font-size: 14.5px;
  max-width: 720px;
}

/* ================= 详情页 ================= */
.detail-card {
  background: #FFFFFF;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 32px 36px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 24px;
}
.detail-breadcrumb {
  font-size: 13px;
  color: var(--color-text-muted);
  margin-bottom: 20px;
}
.detail-breadcrumb a { color: var(--color-text-soft); }
.detail-breadcrumb a:hover { color: var(--color-primary); }
.detail-header {
  border-bottom: 1px solid var(--color-border);
  padding-bottom: 24px;
  margin-bottom: 28px;
}
.detail-title {
  font-size: 26px;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 14px;
  line-height: 1.3;
}
.detail-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
  font-size: 13.5px;
  color: var(--color-text-soft);
}
.detail-meta-item {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}
.detail-meta-item strong {
  color: var(--color-text);
  font-weight: 600;
}
.detail-section { margin-bottom: 32px; }
.detail-section:last-child { margin-bottom: 0; }
.detail-section-title {
  font-size: 17px;
  font-weight: 600;
  color: var(--color-primary);
  margin-bottom: 14px;
  padding-left: 12px;
  border-left: 3px solid var(--color-primary);
}
.detail-section p {
  color: var(--color-text-soft);
  margin-bottom: 12px;
  line-height: 1.8;
}
.detail-section ul, .detail-section ol {
  color: var(--color-text-soft);
  margin-left: 0;
}
.detail-section li {
  margin: 8px 0;
  line-height: 1.7;
}
.detail-fields {
  background: var(--color-bg);
  border-radius: var(--radius-sm);
  padding: 16px 20px;
  border: 1px solid var(--color-border);
  margin-top: 8px;
}

/* ================= 404 页面 ================= */
.notfound {
  text-align: center;
  padding: 80px 20px;
  background: #FFFFFF;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
}
.notfound-code {
  font-size: 80px;
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1;
  margin-bottom: 12px;
}
.notfound-title {
  font-size: 22px;
  color: var(--color-text);
  margin-bottom: 10px;
}
.notfound-desc {
  color: var(--color-text-soft);
  margin-bottom: 24px;
}

/* ================= 新增：详情页样式 ================= */
.page-header {
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-accent) 100%);
  color: #fff;
  padding: 60px 0;
  text-align: center;
}
.page-title {
  font-size: 36px;
  font-weight: 700;
  margin-bottom: 12px;
}
.page-subtitle {
  font-size: 16px;
  opacity: 0.92;
  max-width: 720px;
  margin: 0 auto;
}

.filter-bar {
  display: flex;
  gap: 12px;
  margin-bottom: 24px;
  justify-content: center;
}
.filter-btn {
  padding: 8px 20px;
  background: #fff;
  border: 1px solid var(--color-border);
  border-radius: 20px;
  cursor: pointer;
  font-size: 14px;
  color: var(--color-text);
  transition: all .15s;
}
.filter-btn:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}
.filter-btn.active {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

/* 课程/项目卡片增强 */
.course-card, .project-card {
  display: block;
  text-decoration: none;
  color: inherit;
}
.course-meta-top, .project-meta-top {
  display: flex;
  gap: 8px;
  margin-bottom: 12px;
  flex-wrap: wrap;
}
.course-category, .project-industry {
  font-size: 12px;
  padding: 2px 10px;
  background: #e8f4fd;
  color: var(--color-primary);
  border-radius: 12px;
}
.course-level, .project-level {
  font-size: 12px;
  padding: 2px 10px;
  background: #fef3c7;
  color: #92400e;
  border-radius: 12px;
}
.course-footer, .project-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 16px;
  padding-top: 12px;
  border-top: 1px solid var(--color-border);
  font-size: 13px;
  color: var(--color-text-muted);
}
.course-link, .project-link {
  color: var(--color-primary);
  font-weight: 500;
}

.section-footer {
  text-align: center;
  margin-top: 32px;
}
.section-footer .btn {
  color: var(--color-primary);
  border-color: var(--color-primary);
  background: #fff;
}
.section-footer .btn:hover {
  background: var(--color-primary);
  color: #fff;
}

/* 详情页 */
.back-link {
  display: inline-block;
  margin: 24px 0 16px;
  color: var(--color-text-soft);
  font-size: 14px;
}
.back-link:hover { color: var(--color-primary); }

.detail-header {
  background: #fff;
  padding: 32px;
  border-radius: var(--radius-lg);
  margin-bottom: 24px;
  box-shadow: var(--shadow-sm);
}
.detail-meta {
  display: flex;
  gap: 8px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}
.detail-title {
  font-size: 28px;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: 12px;
}
.detail-summary {
  color: var(--color-text-soft);
  line-height: 1.7;
}
.detail-section {
  background: #fff;
  padding: 24px 32px;
  border-radius: var(--radius-md);
  margin-bottom: 16px;
  box-shadow: var(--shadow-sm);
}
.detail-section-title {
  font-size: 18px;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: 12px;
}
.detail-list {
  padding-left: 20px;
  color: var(--color-text-soft);
  line-height: 1.9;
}
.detail-paragraph {
  color: var(--color-text-soft);
  line-height: 1.8;
}
.detail-actions {
  text-align: center;
  margin: 32px 0;
}
.detail-actions .btn {
  color: #fff;
  background: var(--color-primary);
  border-color: var(--color-primary);
}
.dataset-info { display: grid; gap: 12px; }
.dataset-row { display: flex; gap: 8px; }
.dataset-label { font-weight: 600; color: var(--color-text); min-width: 100px; }
.dataset-fields .dataset-label { margin-bottom: 8px; }

.loading, .error, .empty {
  text-align: center;
  padding: 40px;
  color: var(--color-text-muted);
}
.error { color: #dc2626; }

/* 自我介绍 */
.profile-section { padding: 48px 0; background: var(--color-bg); }
.profile-card {
  display: flex;
  align-items: center;
  gap: 24px;
  background: #fff;
  padding: 32px;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  max-width: 800px;
  margin: 0 auto;
}
.profile-avatar {
  width: 80px;
  height: 80px;
  border-radius: 50%;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 40px;
  flex-shrink: 0;
}
.profile-info { flex: 1; }
.profile-name { font-size: 22px; font-weight: 700; margin-bottom: 4px; }
.profile-school { color: var(--color-text-soft); font-size: 14px; margin-bottom: 2px; }
.profile-major { color: var(--color-primary); font-weight: 500; margin-bottom: 8px; }
.profile-bio { color: var(--color-text-soft); font-size: 14px; line-height: 1.6; }
.profile-badge {
  display: inline-block;
  padding: 2px 12px;
  background: #d1fae5;
  color: #065f46;
  border-radius: 12px;
  font-size: 12px;
  margin-top: 8px;
}

/* Pandas 训练区块 */
.pandas-section { padding: 48px 0; }
@media (max-width: 768px) {
  .page-title { font-size: 26px; }
  .detail-title { font-size: 22px; }
  .profile-card { flex-direction: column; text-align: center; }
  .filter-bar { flex-wrap: wrap; }
}