/* ===== DESIGN SYSTEM — TechPulse Blog ===== */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=Outfit:wght@600;700;800&display=swap');

/* --- CSS Custom Properties --- */
:root {
  /* Colors - Dark Mode (default) */
  --bg-primary: #0a0f1e;
  --bg-secondary: #111827;
  --bg-card: rgba(17, 24, 39, 0.8);
  --bg-card-hover: rgba(30, 41, 59, 0.9);
  --bg-glass: rgba(255, 255, 255, 0.04);
  --border-glass: rgba(255, 255, 255, 0.08);
  --border-hover: rgba(99, 102, 241, 0.4);

  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --text-inverse: #0f172a;

  --accent-primary: #6366f1;
  --accent-primary-hover: #818cf8;
  --accent-secondary: #06b6d4;
  --accent-gradient: linear-gradient(135deg, #6366f1, #06b6d4);
  --accent-gradient-hover: linear-gradient(135deg, #818cf8, #22d3ee);
  --accent-glow: rgba(99, 102, 241, 0.25);

  --success: #22c55e;
  --warning: #f59e0b;
  --error: #ef4444;

  /* Typography */
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-heading: 'Outfit', 'Inter', sans-serif;
  --fs-xs: 0.75rem;
  --fs-sm: 0.875rem;
  --fs-base: 1rem;
  --fs-md: 1.125rem;
  --fs-lg: 1.25rem;
  --fs-xl: 1.5rem;
  --fs-2xl: 1.875rem;
  --fs-3xl: 2.25rem;
  --fs-4xl: 3rem;
  --fs-5xl: 3.75rem;
  --lh-tight: 1.2;
  --lh-normal: 1.6;
  --lh-relaxed: 1.8;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;
  --space-4xl: 6rem;

  /* Border Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.75rem;
  --radius-lg: 1rem;
  --radius-xl: 1.5rem;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.4);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.5);
  --shadow-glow: 0 0 20px var(--accent-glow);

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;

  /* Layout */
  --max-width: 1200px;
  --max-width-article: 780px;
  --header-height: 72px;
  --sidebar-width: 320px;
}

/* --- Light Theme --- */
[data-theme="light"] {
  --bg-primary: #f8fafc;
  --bg-secondary: #ffffff;
  --bg-card: rgba(255, 255, 255, 0.9);
  --bg-card-hover: rgba(241, 245, 249, 1);
  --bg-glass: rgba(0, 0, 0, 0.02);
  --border-glass: rgba(0, 0, 0, 0.08);
  --border-hover: rgba(99, 102, 241, 0.3);
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --text-inverse: #f1f5f9;
  --accent-glow: rgba(99, 102, 241, 0.15);
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-body);
  font-size: var(--fs-base);
  line-height: var(--lh-normal);
  color: var(--text-primary);
  background: var(--bg-primary);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
  transition: background var(--transition-base), color var(--transition-base);
}

img { max-width: 100%; height: auto; display: block; }
a { color: var(--accent-primary); text-decoration: none; transition: color var(--transition-fast); }
a:hover { color: var(--accent-primary-hover); }
ul, ol { list-style: none; }

/* --- Typography --- */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: var(--lh-tight);
  color: var(--text-primary);
}
h1 { font-size: var(--fs-4xl); }
h2 { font-size: var(--fs-3xl); }
h3 { font-size: var(--fs-2xl); }
h4 { font-size: var(--fs-xl); }
p { color: var(--text-secondary); line-height: var(--lh-relaxed); }

/* --- Layout Utilities --- */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}
.section { padding: var(--space-4xl) 0; }
.grid { display: grid; gap: var(--space-xl); }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.flex { display: flex; align-items: center; }
.flex-between { display: flex; align-items: center; justify-content: space-between; }
.text-center { text-align: center; }

/* --- Animations --- */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(24px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}
@keyframes shimmer {
  0% { background-position: -200% 0; }
  100% { background-position: 200% 0; }
}
@keyframes pulse-glow {
  0%, 100% { box-shadow: 0 0 8px var(--accent-glow); }
  50% { box-shadow: 0 0 24px var(--accent-glow); }
}
@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-8px); }
}

.animate-in {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.animate-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* --- Responsive --- */
@media (max-width: 1024px) {
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
  h1 { font-size: var(--fs-3xl); }
}
@media (max-width: 768px) {
  .grid-2, .grid-3 { grid-template-columns: 1fr; }
  .container { padding: 0 var(--space-md); }
  h1 { font-size: var(--fs-2xl); }
  h2 { font-size: var(--fs-xl); }
  .section { padding: var(--space-3xl) 0; }
}