/* === CSS Custom Properties === */
:root {
  --color-primary: #0A2463;
  --color-accent: #2563EB;
  --color-accent-cyan: #06B6D4;
  --color-bg-light: #F8FAFC;
  --color-bg-dark: #0F172A;
  --color-text-dark: #1E293B;
  --color-text-light: #F1F5F9;
  --color-text-muted: #64748B;
  --color-border: #E2E8F0;
  --color-white: #FFFFFF;

  --font-family: "PingFang SC", "Microsoft YaHei", "Noto Sans SC", "Helvetica Neue", Arial, sans-serif;
  --max-width: 1200px;
  --radius: 12px;
  --shadow: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -2px rgba(0,0,0,0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -4px rgba(0,0,0,0.1);
  --transition: 0.3s ease;

  --header-height: 72px;
}

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-family);
  font-size: 16px;
  line-height: 1.7;
  color: var(--color-text-dark);
  background: var(--color-bg-light);
  -webkit-font-smoothing: antialiased;
}

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

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

a:hover {
  color: var(--color-accent-cyan);
}

ul, ol {
  list-style: none;
}

/* === Typography === */
h1, h2, h3, h4, h5, h6 {
  font-weight: 700;
  line-height: 1.3;
  color: var(--color-text-dark);
}

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

p {
  margin-bottom: 1rem;
  color: var(--color-text-muted);
}

/* === Layout === */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.section {
  padding: 80px 0;
}

.section--dark {
  background: var(--color-bg-dark);
  color: var(--color-text-light);
}

.section--dark h1,
.section--dark h2,
.section--dark h3,
.section--dark h4 {
  color: var(--color-white);
}

.section--dark p {
  color: #CBD5E1;
}

.section--alt {
  background: var(--color-white);
}

/* === Section Header === */
.section-header {
  text-align: center;
  margin-bottom: 48px;
}

.section-header h2 {
  font-size: 2rem;
  margin-bottom: 8px;
}

.section-header .subtitle {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 2px;
  margin-bottom: 16px;
}

.section--dark .section-header .subtitle {
  color: var(--color-accent-cyan);
}

.section-header .divider {
  width: 60px;
  height: 3px;
  background: var(--color-accent);
  margin: 0 auto;
  border-radius: 2px;
}

/* === Grid === */
.grid {
  display: grid;
  gap: 24px;
}

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

/* === Scroll Animation === */
.fade-in {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* === Responsive === */
@media (max-width: 1024px) {
  .grid--4 { grid-template-columns: repeat(2, 1fr); }
  .grid--3 { grid-template-columns: repeat(2, 1fr); }
  h1 { font-size: 2rem; }
  h2 { font-size: 1.75rem; }
  .section { padding: 60px 0; }
}

@media (max-width: 768px) {
  .grid--4,
  .grid--3,
  .grid--2 { grid-template-columns: 1fr; }
  h1 { font-size: 1.75rem; }
  h2 { font-size: 1.5rem; }
  .section { padding: 48px 0; }
  :root { --header-height: 60px; }
}

@media (max-width: 480px) {
  .container { padding: 0 16px; }
  .section { padding: 36px 0; }
}