:root {
  --primary: #3B82F6;
  --primary-light: #EFF6FF;
  --primary-dark: #2563EB;
  --primary-soft: #60A5FA;
  --text-main: #0F172A;
  --text-secondary: #64748B;
  --text-light: #94A3B8;
  --bg-body: #F8FAFF;
  --bg-card: #FFFFFF;
  --border: #E2E8F0;
  --border-light: #F1F5F9;
  --shadow-sm: 0 1px 2px rgba(15,23,42,0.04);
  --shadow: 0 4px 12px -2px rgba(15,23,42,0.06), 0 2px 4px -2px rgba(15,23,42,0.04);
  --shadow-lg: 0 16px 32px -8px rgba(37,99,235,0.10), 0 4px 12px -4px rgba(15,23,42,0.06);
  --radius: 14px;
  --radius-sm: 8px;
  --transition: all 0.2s ease;
}

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

body {
  font-family: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background:
    radial-gradient(800px 320px at 50% -80px, rgba(59,130,246,0.08), transparent 70%),
    linear-gradient(180deg, #F6FAFF 0%, #EEF5FF 40%, #FAFCFF 100%);
  background-attachment: fixed;
  color: var(--text-main);
  line-height: 1.6;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

a { text-decoration: none; color: inherit; }
button { font-family: inherit; cursor: pointer; border: none; outline: none; background: none; }

/* ===== 顶部品牌栏 ===== */
.top-header {
  max-width: 1200px;
  margin: 0 auto;
  padding: 20px 24px 0;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-size: 18px;
  font-weight: 700;
  color: var(--primary);
  letter-spacing: 0.2px;
}

.brand-logo {
  height: 60px;
  width: auto;
  object-fit: contain;
}

.brand-text {
  color: var(--text-main);
}

/* ===== Hero 区域 ===== */
.hero-new {
  max-width: 800px;
  margin: 0 auto;
  padding: 48px 24px 32px;
  text-align: center;
}

.hero-title {
  font-size: 42px;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 10px;
  letter-spacing: -0.5px;
}

.hero-subtitle {
  font-size: 16px;
  color: var(--text-secondary);
  margin-bottom: 32px;
}

.hero-search {
  max-width: 680px;
  margin: 0 auto 20px;
  display: flex;
  align-items: center;
  gap: 12px;
  background: #fff;
  border: 1px solid #E8F0FB;
  border-radius: 999px;
  padding: 0 22px;
  height: 56px;
  box-shadow: 0 8px 30px rgba(59, 130, 246, 0.08), 0 2px 8px rgba(15,23,42,0.04);
  transition: var(--transition);
}

.hero-search:focus-within {
  box-shadow: 0 10px 36px rgba(59, 130, 246, 0.14), 0 2px 8px rgba(15,23,42,0.04);
  border-color: var(--primary-soft);
}

.hero-search svg {
  color: var(--primary-soft);
  flex-shrink: 0;
}

.hero-search input {
  border: none;
  background: transparent;
  outline: none;
  flex: 1;
  font-size: 15px;
  color: var(--text-main);
}

.hero-search input::placeholder {
  color: var(--text-light);
}

/* ===== 分类 Tab ===== */
.category-tabs {
  max-width: 1200px;
  margin: 0 auto;
  padding: 24px 24px 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 36px;
  flex-wrap: wrap;
}

.category-tabs .tab {
  font-size: 15px;
  font-weight: 500;
  color: var(--text-secondary);
  padding: 6px 4px;
  position: relative;
  transition: var(--transition);
  letter-spacing: 0.3px;
}

.category-tabs .tab:hover {
  color: var(--primary);
}

.category-tabs .tab.active {
  color: var(--primary);
  font-weight: 600;
}

.category-tabs .tab.active::after {
  content: '';
  position: absolute;
  left: 0;
  right: 0;
  bottom: -4px;
  height: 3px;
  background: linear-gradient(90deg, var(--primary), var(--primary-soft));
  border-radius: 2px;
}

/* ===== 资源列表 ===== */
.main-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 16px 24px 48px;
}

.section-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 24px;
}

.section-header h2 {
  font-size: 20px;
  font-weight: 700;
  color: var(--text-main);
  letter-spacing: -0.2px;
}

.result-count {
  font-size: 14px;
  color: var(--text-light);
}

.resource-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
}

.resource-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  transition: var(--transition);
  display: flex;
  flex-direction: column;
  gap: 12px;
  box-shadow: var(--shadow-sm);
}

.resource-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-3px);
  border-color: #DBEAFE;
}

.card-icon {
  width: 48px;
  height: 48px;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.card-icon.pdf { background: #FEF2F2; color: #EF4444; }
.card-icon.word { background: #EFF6FF; color: #3B82F6; }
.card-icon.image { background: #F0FDF4; color: #10B981; }
.card-icon.link { background: #FFFBEB; color: #F59E0B; }
.card-icon.mindmap { background: #F5F3FF; color: #8B5CF6; }
.card-icon.file { background: #F8FAFC; color: #64748B; }

.card-title {
  font-size: 16px;
  font-weight: 600;
  color: var(--text-main);
  line-height: 1.4;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.card-desc {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.5;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
  flex: 1;
}

.card-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 8px;
  border-top: 1px solid var(--border-light);
}

.card-category {
  font-size: 12px;
  color: var(--text-secondary);
  background: var(--border-light);
  padding: 4px 10px;
  border-radius: 12px;
}

.card-actions {
  display: flex;
  gap: 8px;
}

.btn-card {
  padding: 6px 14px;
  border-radius: 6px;
  font-size: 13px;
  font-weight: 500;
  transition: var(--transition);
  display: flex;
  align-items: center;
  gap: 4px;
}

.btn-preview {
  background: var(--primary-light);
  color: var(--primary);
}

.btn-preview:hover { background: var(--primary); color: #fff; }

.btn-download {
  background: var(--bg-body);
  color: var(--text-secondary);
}

.btn-download:hover {
  background: var(--text-main);
  color: #fff;
}

/* ===== 空状态 ===== */
.empty-state {
  text-align: center;
  padding: 64px 24px;
  color: var(--text-light);
}

.empty-state svg {
  margin-bottom: 16px;
  opacity: 0.4;
}

.empty-state p { font-size: 16px; }

/* ===== 预览弹窗 ===== */
.modal-overlay {
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  background: rgba(15,23,42,0.5);
  backdrop-filter: blur(4px);
  z-index: 1000;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 24px;
}

.modal-overlay.active { display: flex; }

.modal-container {
  background: #fff;
  border-radius: var(--radius);
  width: 100%;
  max-width: 900px;
  height: 85vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  box-shadow: 0 24px 64px rgba(15,23,42,0.24);
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

.modal-header h3 {
  font-size: 18px;
  font-weight: 600;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  max-width: 400px;
}

.modal-actions {
  display: flex;
  align-items: center;
  gap: 8px;
}

.btn-modal-download, .btn-modal-link {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  border-radius: 6px;
  font-size: 14px;
  font-weight: 500;
  transition: var(--transition);
}

.btn-modal-download {
  background: var(--primary);
  color: #fff;
}

.btn-modal-download:hover { background: var(--primary-dark); }

.btn-modal-link {
  background: var(--bg-body);
  color: var(--text-secondary);
}

.btn-modal-link:hover { background: var(--border); }

.modal-close {
  background: transparent;
  color: var(--text-secondary);
  padding: 4px;
  border-radius: 6px;
  transition: var(--transition);
  display: flex;
}

.modal-close:hover {
  background: var(--bg-body);
  color: var(--text-main);
}

.modal-body {
  flex: 1;
  overflow: hidden;
  position: relative;
}

.modal-body iframe {
  width: 100%;
  height: 100%;
  border: none;
}

.modal-body img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  background: var(--bg-body);
}

.modal-body .preview-info {
  padding: 40px;
  text-align: center;
  color: var(--text-secondary);
}

.modal-body .preview-info svg {
  margin-bottom: 16px;
  color: var(--primary);
}

.preview-info h4 {
  font-size: 18px;
  color: var(--text-main);
  margin-bottom: 8px;
}

.preview-info p { font-size: 14px; margin-bottom: 24px; }

.preview-info .btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 28px;
  background: var(--primary);
  color: #fff;
  border-radius: 8px;
  font-size: 15px;
  font-weight: 500;
  transition: var(--transition);
}

.preview-info .btn-primary:hover { background: var(--primary-dark); }

/* ===== 页脚 ===== */
.footer {
  text-align: center;
  padding: 32px 24px;
  color: var(--text-light);
  font-size: 14px;
  background: transparent;
}

/* ===== 响应式 ===== */
@media (max-width: 768px) {
  .top-header { padding: 16px 16px 0; }
  .hero-new { padding: 36px 16px 24px; }
  .hero-title { font-size: 30px; }
  .hero-subtitle { font-size: 14px; margin-bottom: 24px; }
  .hero-search { height: 50px; padding: 0 16px; }
  .category-tabs { gap: 24px; padding: 16px 16px 12px; }
  .category-tabs .tab { font-size: 14px; }
  .main-content { padding: 12px 16px 40px; }
  .resource-grid { grid-template-columns: 1fr; }
  .modal-container { height: 90vh; }
}