/* ============================================
   EXCEL ANALYST HUB — DESIGN SYSTEM
   main.css: Variables, Reset, Typography, Layout, Animations
   ============================================ */

/* --- Google Fonts --- */
@import url('https://fonts.googleapis.com/css2?family=Sora:wght@400;500;600;700;800&family=DM+Sans:ital,opsz,wght@0,9..40,300;0,9..40,400;0,9..40,500;0,9..40,600;1,9..40,400&family=JetBrains+Mono:wght@400;500;600&display=swap');

/* --- CSS Variables (Dark mode = default) --- */
:root,
[data-theme="dark"] {
  /* Colors */
  --bg: #0f1117;
  --surface: #1a1d27;
  --surface-2: #22253a;
  --border: #2a2d3a;
  --accent: #4f8ef7;
  --accent-2: #7c3aed;
  --text: #e8eaf0;
  --text-muted: #8b8fa8;
  --success: #22c55e;
  --warning: #f59e0b;
  --danger: #ef4444;

  /* Typography */
  --font-display: 'Sora', system-ui, sans-serif;
  --font-body: 'DM Sans', system-ui, sans-serif;
  --font-mono: 'JetBrains Mono', 'Courier New', monospace;

  /* Spacing */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;
  --space-16: 64px;
  --space-20: 80px;
  --space-24: 96px;

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

  /* Borders */
  --radius-sm: 4px;
  --radius: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-pill: 999px;

  /* Shadows */
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.4);
  --shadow: 0 4px 16px rgba(0,0,0,0.3);
  --shadow-lg: 0 8px 32px rgba(0,0,0,0.4);
  --shadow-accent: 0 4px 24px rgba(79,142,247,0.15);
  --shadow-hover: 0 8px 32px rgba(0,0,0,0.5);

  /* Transitions */
  --transition: 200ms ease;
  --transition-slow: 400ms ease;
}

/* --- Light Mode Variables --- */
[data-theme="light"] {
  --bg: #ffffff;
  --surface: #f5f5f5;
  --surface-2: #ebebeb;
  --border: #ddd;
  --accent: #2563eb;
  --accent-2: #7c3aed;
  --text: #1a1a2e;
  --text-muted: #555;
  --success: #16a34a;
  --warning: #d97706;
  --danger: #dc2626;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow: 0 4px 16px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 32px rgba(0,0,0,0.12);
  --shadow-accent: 0 4px 24px rgba(37,99,235,0.15);
  --shadow-hover: 0 8px 32px rgba(0,0,0,0.15);
}


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

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

body {
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.75;
  color: var(--text);
  background-color: var(--bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

img, video, svg {
  display: block;
  max-width: 100%;
}

a {
  color: var(--accent);
  text-decoration: none;
  transition: color var(--transition);
}
a:hover {
  color: #7aaeff;
}

ul, ol {
  list-style: none;
}

button {
  cursor: pointer;
  font-family: var(--font-body);
  border: none;
  background: none;
}

input, select, textarea {
  font-family: var(--font-body);
  font-size: 1rem;
}

/* --- Typography Scale --- */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-display);
  color: var(--text);
  line-height: 1.2;
  font-weight: 700;
  letter-spacing: -0.01em;
}

h1 { font-size: clamp(2rem, 5vw, 3.25rem); font-weight: 800; }
h2 { font-size: clamp(1.5rem, 3.5vw, 2.25rem); font-weight: 700; }
h3 { font-size: clamp(1.125rem, 2.5vw, 1.5rem); font-weight: 600; }
h4 { font-size: 1.125rem; font-weight: 600; }
h5 { font-size: 1rem; font-weight: 600; }

p {
  color: var(--text);
  line-height: 1.8;
}

.text-muted {
  color: var(--text-muted);
}

.text-accent {
  color: var(--accent);
}

.text-success { color: var(--success); }
.text-warning { color: var(--warning); }
.text-danger  { color: var(--danger); }

code, .formula, kbd {
  font-family: var(--font-mono);
  font-size: 0.875em;
}

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

@media (max-width: 768px) {
  .container { padding: 0 var(--space-4); }
}

.section {
  padding: var(--space-20) 0;
}

.section-sm {
  padding: var(--space-12) 0;
}

.section-header {
  margin-bottom: var(--space-10);
}

.section-header h2 {
  margin-bottom: var(--space-3);
}

.section-header p {
  color: var(--text-muted);
  max-width: 560px;
}

/* Grid Layouts */
.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-6);
}

.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-6);
}

.grid-auto {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-6);
}

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

@media (max-width: 640px) {
  .grid-3, .grid-2 {
    grid-template-columns: 1fr;
  }
}

/* Flex Utilities */
.flex { display: flex; }
.flex-center {
  display: flex;
  align-items: center;
  justify-content: center;
}
.flex-between {
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.flex-start {
  display: flex;
  align-items: center;
  justify-content: flex-start;
  gap: var(--space-3);
}
.flex-col {
  display: flex;
  flex-direction: column;
}
.gap-2 { gap: var(--space-2); }
.gap-3 { gap: var(--space-3); }
.gap-4 { gap: var(--space-4); }
.gap-6 { gap: var(--space-6); }

/* Spacing Utilities */
.mt-2 { margin-top: var(--space-2); }
.mt-3 { margin-top: var(--space-3); }
.mt-4 { margin-top: var(--space-4); }
.mt-6 { margin-top: var(--space-6); }
.mt-8 { margin-top: var(--space-8); }
.mb-2 { margin-bottom: var(--space-2); }
.mb-3 { margin-bottom: var(--space-3); }
.mb-4 { margin-bottom: var(--space-4); }
.mb-6 { margin-bottom: var(--space-6); }
.mb-8 { margin-bottom: var(--space-8); }

/* --- Page scroll offset for fixed nav --- */
section[id], [id].scroll-target {
  scroll-margin-top: calc(var(--nav-height) + 16px);
}

/* ============================================
   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 {
  from { background-position: -200% center; }
  to   { background-position: 200% center; }
}

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

@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* Fade-in utility classes */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

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

/* Staggered animation delays */
.delay-1 { transition-delay: 0.1s; animation-delay: 0.1s; }
.delay-2 { transition-delay: 0.2s; animation-delay: 0.2s; }
.delay-3 { transition-delay: 0.3s; animation-delay: 0.3s; }
.delay-4 { transition-delay: 0.4s; animation-delay: 0.4s; }
.delay-5 { transition-delay: 0.5s; animation-delay: 0.5s; }
.delay-6 { transition-delay: 0.6s; animation-delay: 0.6s; }

/* Hero animation class */
.animate-hero {
  animation: fadeInUp 0.7s ease forwards;
}

/* ============================================
   DIVIDERS & MISC
   ============================================ */
.divider {
  border: none;
  border-top: 1px solid var(--border);
  margin: var(--space-8) 0;
}

.hidden { display: none !important; }
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0,0,0,0);
  white-space: nowrap;
}

/* Gradient text */
.gradient-text {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}