/* CSS Variables */
:root {
  --ui-ink: #101827;
  --ui-primary: #2458e6;
  --ui-page: #fbfaf7;
  --ui-surface: #ffffff;
  --ui-subtle: #f4f2ee;
  --ui-border: #e4e7ec;
  --ui-muted: #667085;
  --color-primary: #0066cc;
  --color-primary-dark: #0052a3;
  --color-text: #333;
  --color-text-light: #666;
  --color-text-lighter: #999;
  --color-bg: #fff;
  --color-bg-gray: #f8f9fa;
  --color-border: #e0e0e0;
  --color-success: #28a745;
  --color-warning: #ffc107;
  --color-danger: #dc3545;
  
  --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  
  --spacing-xs: 8px;
  --spacing-sm: 16px;
  --spacing-md: 24px;
  --spacing-lg: 32px;
  --spacing-xl: 48px;
  --spacing-xxl: 64px;
  
  --border-radius: 4px;
  --border-radius-lg: 8px;
  
  --shadow-sm: 0 2px 4px rgba(0,0,0,0.1);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.12);
  
  --transition: all 0.3s ease;
}

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

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

body {
  font-family: var(--font-family);
  line-height: 1.6;
  color: var(--color-text);
  background: var(--ui-page);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

main { min-height: 55vh; }

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.3;
  color: var(--color-text);
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }
h5 { font-size: 1.125rem; }
h6 { font-size: 1rem; }

p {
  margin-bottom: var(--spacing-sm);
  color: var(--color-text-light);
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: var(--transition);
}

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

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

ul, ol {
  margin-bottom: var(--spacing-sm);
  padding-left: var(--spacing-md);
}

li {
  margin-bottom: var(--spacing-xs);
}

/* Layout */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

.section {
  padding: var(--spacing-xxl) 0;
}

.section-gray {
  background: var(--color-bg-gray);
}

.section-title {
  text-align: center;
  font-size: 2rem;
  margin-bottom: var(--spacing-lg);
  position: relative;
}

.section-title::after {
  content: '';
  display: block;
  width: 60px;
  height: 3px;
  background: var(--color-primary);
  margin: 15px auto 0;
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 12px 32px;
  border-radius: var(--border-radius);
  font-size: 1rem;
  font-weight: 500;
  text-align: center;
  cursor: pointer;
  transition: var(--transition);
  border: none;
}

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

.btn-primary:hover {
  background: var(--color-primary-dark);
  color: white;
}

.btn-secondary {
  background: transparent;
  border: 1px solid var(--color-primary);
  color: var(--color-primary);
}

.btn-secondary:hover {
  background: var(--color-primary);
  color: white;
}

.btn-lg {
  padding: 16px 40px;
  font-size: 1.125rem;
}

.btn-sm {
  padding: 8px 20px;
  font-size: 0.875rem;
}

/* Grid */
.grid {
  display: grid;
  gap: var(--spacing-md);
}

.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }

/* Cards */
.card {
  background: var(--color-bg);
  border-radius: var(--border-radius-lg);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  transition: var(--transition);
}

.card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-4px);
}

.card-img {
  width: 100%;
  height: 200px;
  object-fit: cover;
}

.card-body {
  padding: var(--spacing-md);
}

.card-title {
  font-size: 1.25rem;
  margin-bottom: var(--spacing-xs);
}

.card-text {
  color: var(--color-text-light);
  font-size: 0.875rem;
  line-height: 1.6;
}

/* Utilities */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mt-0 { margin-top: 0; }
.mt-1 { margin-top: var(--spacing-xs); }
.mt-2 { margin-top: var(--spacing-sm); }
.mt-3 { margin-top: var(--spacing-md); }
.mt-4 { margin-top: var(--spacing-lg); }
.mt-5 { margin-top: var(--spacing-xl); }

.mb-0 { margin-bottom: 0; }
.mb-1 { margin-bottom: var(--spacing-xs); }
.mb-2 { margin-bottom: var(--spacing-sm); }
.mb-3 { margin-bottom: var(--spacing-md); }
.mb-4 { margin-bottom: var(--spacing-lg); }
.mb-5 { margin-bottom: var(--spacing-xl); }

.py-1 { padding-top: var(--spacing-xs); padding-bottom: var(--spacing-xs); }
.py-2 { padding-top: var(--spacing-sm); padding-bottom: var(--spacing-sm); }
.py-3 { padding-top: var(--spacing-md); padding-bottom: var(--spacing-md); }
.py-4 { padding-top: var(--spacing-lg); padding-bottom: var(--spacing-lg); }
.py-5 { padding-top: var(--spacing-xl); padding-bottom: var(--spacing-xl); }

/* Responsive */
@media (max-width: 768px) {
  html { font-size: 14px; }
  
  h1 { font-size: 2rem; }
  h2 { font-size: 1.75rem; }
  h3 { font-size: 1.25rem; }
  
  .grid-2, .grid-3, .grid-4 {
    grid-template-columns: 1fr;
  }
  
  .section {
    padding: var(--spacing-xl) 0;
  }
  
  .section-title {
    font-size: 1.5rem;
  }
}

@media (min-width: 769px) and (max-width: 1024px) {
  .grid-3, .grid-4 {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* Animations */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

.fade-in {
  animation: fadeIn 0.6s ease forwards;
}

/* Loading skeleton */
.skeleton {
  background: linear-gradient(90deg, #f0f0f0 25%, #e0e0e0 50%, #f0f0f0 75%);
  background-size: 200% 100%;
  animation: skeleton-loading 1.5s infinite;
}

@keyframes skeleton-loading {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* Accessibility */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* Print styles */
@media print {
  .no-print {
    display: none;
  }
}