/* ===== CSS Variables & Reset ===== */
:root {
  --primary: #2563eb;
  --primary-light: #3b82f6;
  --primary-dark: #1d4ed8;
  --primary-container: #dbeafe;
  --on-primary: #ffffff;
  --surface: #ffffff;
  --surface-container: #f8fafc;
  --surface-container-lowest: #f1f5f9;
  --on-surface: #0f172a;
  --on-surface-variant: #475569;
  --outline: #cbd5e1;
  --border: #e2e8f0;
  --bg-background: #ffffff;
  --radius: 8px;
  --radius-lg: 12px;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;
  color: var(--on-surface);
  background: var(--bg-background);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a {
  color: inherit;
  text-decoration: none;
  transition: color 0.2s;
}

a:hover {
  color: var(--primary);
}

img {
  max-width: 100%;
  height: auto;
}

/* ===== Layout ===== */
.page-gutter {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

.bleed-section {
  width: 100%;
}

/* ===== Header ===== */
header {
  position: sticky;
  top: 0;
  z-index: 50;
  width: 100%;
  border-bottom: 1px solid var(--border);
  background: rgba(255,255,255,0.9);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

header .header-inner {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  height: 56px;
  gap: 16px;
}

header .logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--primary);
}

header .logo svg {
  width: 32px;
  height: auto;
}

header nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 24px;
}

header nav a {
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--on-surface-variant);
  padding: 4px 0;
  position: relative;
}

header nav a:hover,
header nav a.active {
  color: var(--primary);
}

header nav a.active::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--primary);
  border-radius: 1px;
}

/* ===== Hero Section ===== */
.hero {
  position: relative;
  overflow: hidden;
  background: var(--bg-background);
  padding: 80px 0 56px;
}

.hero-grid {
  position: absolute;
  inset: 0;
  background-image: 
    linear-gradient(rgba(37,99,235,0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(37,99,235,0.03) 1px, transparent 1px);
  background-size: 40px 40px;
  pointer-events: none;
}

.hero-glow {
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse 80% 60% at 50% -10%, color-mix(in srgb, var(--primary) 14%, transparent), transparent);
  pointer-events: none;
}

.hero-bottom-fade {
  position: absolute;
  inset-x: 0;
  bottom: 0;
  height: 128px;
  background: linear-gradient(to top, var(--bg-background), transparent);
  pointer-events: none;
}

.hero-content {
  position: relative;
  text-align: center;
  max-width: 768px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 24px;
}

.hero-content h1 {
  font-size: 2.25rem;
  line-height: 1.12;
  letter-spacing: -0.02em;
  color: var(--primary);
  font-weight: 800;
}

.hero-content p {
  font-size: 1.125rem;
  color: var(--on-surface-variant);
  max-width: 600px;
  line-height: 1.75;
}

.hero-buttons {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  justify-content: center;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  min-height: 40px;
  padding: 8px 24px;
  border-radius: var(--radius);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: all 0.2s;
  text-decoration: none;
}

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

.btn-primary:hover {
  opacity: 0.9;
  color: var(--on-primary);
}

.btn-outline {
  background: var(--surface);
  border: 1px solid var(--outline);
  color: var(--on-surface);
}

.btn-outline:hover {
  border-color: var(--primary-light);
  color: var(--primary);
}

.btn svg {
  width: 16px;
  height: 16px;
  flex-shrink: 0;
}

/* ===== Hot Tags ===== */
.hot-tags {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 8px;
  margin-top: 20px;
  font-size: 0.8125rem;
  color: var(--on-surface-variant);
}

.hot-tags .label {
  font-weight: 500;
}

.tag {
  display: inline-block;
  padding: 4px 12px;
  border-radius: 999px;
  border: 1px solid var(--outline);
  background: var(--surface);
  font-size: 0.8125rem;
  color: var(--on-surface-variant);
  transition: all 0.2s;
  cursor: pointer;
  text-decoration: none;
}

.tag:hover {
  border-color: var(--primary-light);
  color: var(--primary);
}

/* ===== Stats Section ===== */
.stats-section {
  position: relative;
  overflow: hidden;
  border-bottom: 1px solid var(--border);
  background: var(--surface-container-lowest);
  padding: 40px 0 64px;
}

.stats-title {
  text-align: center;
  margin-bottom: 8px;
}

.stats-title h2 {
  font-size: 1.375rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--on-surface);
}

.stats-title p {
  font-size: 1.0625rem;
  color: var(--on-surface-variant);
  margin-top: 4px;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
  max-width: 900px;
  margin: 40px auto 0;
}

.stat-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 24px;
  border-radius: var(--radius-lg);
  background: var(--primary-container);
  text-align: center;
}

.stat-number {
  font-size: 2.5rem;
  font-weight: 800;
  line-height: 1;
  letter-spacing: -0.02em;
  color: var(--primary);
}

.stat-label {
  margin-top: 8px;
  font-size: 1rem;
  color: var(--on-surface-variant);
}

/* ===== Resource List Section ===== */
.resource-section {
  padding: 48px 0 64px;
}

.resource-section h2 {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 24px;
  text-align: center;
}

.resource-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
}

.resource-card {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  transition: all 0.2s;
  background: var(--surface);
}

.resource-card:hover {
  border-color: var(--primary-light);
  box-shadow: 0 4px 12px rgba(37,99,235,0.08);
  transform: translateY(-2px);
}

.resource-card h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--on-surface);
}

.resource-card .meta {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 12px;
  font-size: 0.8125rem;
}

.resource-card .meta span {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 2px 8px;
  border-radius: 4px;
  background: var(--surface-container);
  color: var(--on-surface-variant);
}

.resource-card .download-btn {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--primary);
  padding: 6px 16px;
  border-radius: var(--radius);
  border: 1px solid var(--primary);
  background: transparent;
  cursor: pointer;
  transition: all 0.2s;
}

.resource-card .download-btn:hover {
  background: var(--primary);
  color: var(--on-primary);
}

/* ===== Search Page ===== */
.search-section {
  padding: 32px 0 48px;
}

.search-box {
  display: flex;
  gap: 12px;
  margin-bottom: 24px;
}

.search-box input {
  flex: 1;
  padding: 10px 16px;
  border: 1px solid var(--outline);
  border-radius: var(--radius);
  font-size: 1rem;
  outline: none;
  transition: border-color 0.2s;
}

.search-box input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37,99,235,0.1);
}

.search-box button {
  padding: 10px 24px;
  background: var(--primary);
  color: var(--on-primary);
  border: none;
  border-radius: var(--radius);
  font-size: 0.9375rem;
  font-weight: 600;
  cursor: pointer;
  transition: opacity 0.2s;
}

.search-box button:hover {
  opacity: 0.9;
}

/* ===== Filter Sidebar ===== */
.filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 24px;
}

.filter-group {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.filter-group label {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--on-surface-variant);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.filter-group select {
  padding: 6px 12px;
  border: 1px solid var(--outline);
  border-radius: var(--radius);
  font-size: 0.875rem;
  background: var(--surface);
  cursor: pointer;
}

/* ===== Footer ===== */
footer {
  margin-top: auto;
  border-top: 1px solid var(--border);
  padding: 16px 0;
}

footer nav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
  gap: 16px;
  margin-bottom: 8px;
}

footer nav a {
  font-size: 0.8125rem;
  color: var(--on-surface-variant);
}

footer p {
  text-align: center;
  font-size: 0.8125rem;
  color: var(--on-surface-variant);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .hero-content h1 {
    font-size: 1.75rem;
  }
  
  .hero-content p {
    font-size: 1rem;
  }
  
  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
  }
  
  .stat-number {
    font-size: 2rem;
  }
  
  header nav {
    gap: 12px;
  }
  
  header nav a {
    font-size: 0.8125rem;
  }
  
  .resource-grid {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 480px) {
  .hero {
    padding: 48px 0 32px;
  }
  
  .hero-buttons {
    flex-direction: column;
    width: 100%;
  }
  
  .hero-buttons .btn {
    width: 100%;
    justify-content: center;
  }
  
  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
  }
  
  .stat-card {
    padding: 16px;
  }
}

/* ===== Breadcrumb ===== */
.breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.875rem;
  color: var(--on-surface-variant);
  margin-bottom: 24px;
  padding: 16px 0 0;
}

.breadcrumb a {
  color: var(--on-surface-variant);
}

.breadcrumb a:hover {
  color: var(--primary);
}

.breadcrumb .separator {
  color: var(--outline);
}

/* ===== Page Header ===== */
.page-header {
  padding: 24px 0;
  border-bottom: 1px solid var(--border);
  margin-bottom: 32px;
}

.page-header h1 {
  font-size: 2rem;
  font-weight: 800;
  color: var(--on-surface);
}

.page-header p {
  color: var(--on-surface-variant);
  margin-top: 4px;
}