/* ========================================
   DESIGN SYSTEM — How LLM Works
   ======================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800;900&family=JetBrains+Mono:wght@400;500;600&display=swap');

/* --- CSS Custom Properties --- */
:root {
  /* Colors */
  --bg-primary: #0a0a0f;
  --bg-secondary: #12121a;
  --bg-card: rgba(255, 255, 255, 0.04);
  --bg-card-hover: rgba(255, 255, 255, 0.08);
  --bg-glass: rgba(255, 255, 255, 0.06);
  --bg-glass-border: rgba(255, 255, 255, 0.1);

  --text-primary: #f0f0f5;
  --text-secondary: rgba(240, 240, 245, 0.7);
  --text-muted: rgba(240, 240, 245, 0.45);

  --accent-blue: #4F8EF7;
  --accent-violet: #8B5CF6;
  --accent-cyan: #06B6D4;
  --accent-coral: #F97316;
  --accent-green: #22C55E;
  --accent-pink: #EC4899;

  --gradient-primary: linear-gradient(135deg, #4F8EF7 0%, #8B5CF6 100%);
  --gradient-secondary: linear-gradient(135deg, #06B6D4 0%, #4F8EF7 100%);
  --gradient-warm: linear-gradient(135deg, #F97316 0%, #EC4899 100%);
  --gradient-hero: linear-gradient(135deg, rgba(79, 142, 247, 0.15) 0%, rgba(139, 92, 246, 0.15) 50%, rgba(6, 182, 212, 0.1) 100%);

  --correct: #22C55E;
  --incorrect: #EF4444;

  /* Typography */
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

  --fs-xs: 0.75rem;
  --fs-sm: 0.875rem;
  --fs-base: 1rem;
  --fs-lg: 1.125rem;
  --fs-xl: 1.25rem;
  --fs-2xl: 1.5rem;
  --fs-3xl: 1.875rem;
  --fs-4xl: 2.25rem;
  --fs-5xl: 3rem;
  --fs-6xl: 3.75rem;
  --fs-hero: clamp(2.5rem, 6vw, 5rem);

  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;

  /* Borders */
  --radius-sm: 0.375rem;
  --radius-md: 0.75rem;
  --radius-lg: 1rem;
  --radius-xl: 1.5rem;
  --radius-2xl: 2rem;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.5);
  --shadow-glow-blue: 0 0 20px rgba(79, 142, 247, 0.3);
  --shadow-glow-violet: 0 0 20px rgba(139, 92, 246, 0.3);
  --shadow-glow-cyan: 0 0 20px rgba(6, 182, 212, 0.3);

  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 300ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 500ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-spring: 500ms cubic-bezier(0.34, 1.56, 0.64, 1);

  /* Layout */
  --max-width: 1200px;
  --sidebar-width: 280px;
  --nav-height: 64px;
}

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-size: 16px;
}

body {
  font-family: var(--font-body);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  overflow-x: hidden;
  min-height: 100vh;
}

/* --- Typography Defaults --- */
h1, h2, h3, h4, h5, h6 {
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.02em;
}

h1 { font-size: var(--fs-hero); font-weight: 900; }
h2 { font-size: var(--fs-4xl); }
h3 { font-size: var(--fs-2xl); }
h4 { font-size: var(--fs-xl); }

p {
  color: var(--text-secondary);
  line-height: 1.8;
  max-width: 72ch;
}

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

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

code, pre {
  font-family: var(--font-mono);
}

code {
  background: var(--bg-card);
  padding: 0.15em 0.4em;
  border-radius: var(--radius-sm);
  font-size: 0.9em;
  color: var(--accent-cyan);
}

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

ul, ol {
  list-style: none;
}

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

input, textarea, select {
  font-family: inherit;
  outline: none;
  border: none;
  background: none;
  color: inherit;
}

::selection {
  background: rgba(79, 142, 247, 0.3);
  color: var(--text-primary);
}

::-webkit-scrollbar {
  width: 6px;
}

::-webkit-scrollbar-track {
  background: var(--bg-secondary);
}

::-webkit-scrollbar-thumb {
  background: rgba(255, 255, 255, 0.15);
  border-radius: var(--radius-full);
}

::-webkit-scrollbar-thumb:hover {
  background: rgba(255, 255, 255, 0.25);
}

/* --- Utility Classes --- */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-6);
}

.gradient-text {
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.gradient-text-secondary {
  background: var(--gradient-secondary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.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;
}

/* --- Animations --- */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes slideInLeft {
  from {
    opacity: 0;
    transform: translateX(-30px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

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

@keyframes rotate {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

@keyframes scaleIn {
  from {
    opacity: 0;
    transform: scale(0.9);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

.animate-in {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

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