/* ============================================
   Big Tech Design System
   Minimalist, world-class aesthetic
   ============================================ */

:root {
  /* Typography */
  --font-system: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif;
  --font-mono: 'SF Mono', Monaco, 'Cascadia Code', 'Roboto Mono', Consolas, 'Courier New', monospace;
  
  /* Colors - Minimalist Big Tech Palette */
  --color-bg: #ffffff;
  --color-surface: #fafafa;
  --color-surface-elevated: #ffffff;
  --color-text: #1a1a1a;
  --color-text-secondary: #666666;
  --color-text-muted: #999999;
  --color-border: #e5e5e5;
  --color-border-subtle: #f0f0f0;
  
  /* Accent - Professional Blue */
  --color-primary: #0066cc;
  --color-primary-dark: #0052a3;
  --color-primary-light: #e6f2ff;
  
  /* Semantic */
  --color-success: #00a86b;
  --color-warning: #ff9500;
  
  /* Spacing */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;
  --space-3xl: 64px;
  
  /* Typography Scale */
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 2rem;
  --text-4xl: 2.5rem;
  --text-5xl: 3rem;
  
  /* Layout */
  --max-width: 1200px;
  --max-width-narrow: 800px;
  --border-radius: 8px;
  --border-radius-lg: 12px;
  
  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.07);
  --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 20px 25px rgba(0, 0, 0, 0.1);
  
  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 350ms ease;
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #0a0a0a;
    --color-surface: #111111;
    --color-surface-elevated: #1a1a1a;
    --color-text: #e5e5e5;
    --color-text-secondary: #b3b3b3;
    --color-text-muted: #808080;
    --color-border: #2a2a2a;
    --color-border-subtle: #1f1f1f;
    --color-primary-light: #001a33;
  }
}

/* Dark Mode Class (for manual toggle) */
html.dark-mode {
  --color-bg: #0a0a0a;
  --color-surface: #111111;
  --color-surface-elevated: #1a1a1a;
  --color-text: #e5e5e5;
  --color-text-secondary: #b3b3b3;
  --color-text-muted: #808080;
  --color-border: #2a2a2a;
  --color-border-subtle: #1f1f1f;
  --color-primary-light: #001a33;
}

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

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

body {
  font-family: var(--font-system);
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
  transition: background-color var(--transition-base), color var(--transition-base);
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.2;
  letter-spacing: -0.02em;
  color: var(--color-text);
}

h1 { font-size: var(--text-4xl); }
h2 { font-size: var(--text-3xl); margin-bottom: var(--space-lg); }
h3 { font-size: var(--text-2xl); margin-bottom: var(--space-md); }
h4 { font-size: var(--text-xl); }
h5 { font-size: var(--text-lg); }
h6 { font-size: var(--text-base); }

p {
  margin-bottom: var(--space-md);
  color: var(--color-text-secondary);
}

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

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

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

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

button {
  font-family: inherit;
  border: none;
  background: none;
  cursor: pointer;
  padding: 0;
}

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

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

.container-narrow {
  max-width: var(--max-width-narrow);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

/* Navigation */
nav {
  position: sticky;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(250, 250, 250, 0.95);
  backdrop-filter: blur(20px) saturate(180%);
  border-bottom: 1px solid var(--color-border);
  transition: all var(--transition-base);
}

nav.scrolled {
  box-shadow: var(--shadow-md);
}

@media (prefers-color-scheme: dark) {
  nav {
    background: rgba(10, 10, 10, 0.95);
  }
}

html.dark-mode nav {
  background: rgba(10, 10, 10, 0.95);
}

.nav-container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-lg) var(--space-xl);
  display: flex;
  justify-content: space-between;
  align-items: center;
  min-height: 70px;
}

.brand {
  font-weight: 700;
  font-size: var(--text-xl);
  letter-spacing: -0.01em;
  color: var(--color-text);
  padding: var(--space-xs) var(--space-sm);
  display: inline-block;
}

.nav-links {
  display: flex;
  gap: var(--space-lg);
  align-items: center;
}

.nav-links a {
  font-size: var(--text-base);
  font-weight: 500;
  color: var(--color-text-secondary);
  padding: var(--space-sm) var(--space-md);
  position: relative;
  display: inline-block;
  min-height: 44px;
  display: flex;
  align-items: center;
}

.nav-links a:hover {
  color: var(--color-text);
}

.nav-links a.active {
  color: var(--color-text);
}

.nav-links a.active::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--color-primary);
}

/* Dark Mode Toggle */
.dark-mode-toggle {
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--border-radius);
  border: 1px solid var(--color-border);
  background: var(--color-surface-elevated);
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
  margin-left: var(--space-md);
}

.dark-mode-toggle:hover {
  background: var(--color-surface);
  color: var(--color-text);
}

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

/* Hero Section */
.hero {
  padding: calc(80px + var(--space-3xl)) 0 var(--space-3xl);
  text-align: center;
}

.hero-content {
  max-width: 800px;
  margin: 0 auto;
}

.hero h1 {
  font-size: clamp(var(--text-3xl), 5vw, var(--text-5xl));
  font-weight: 700;
  margin-bottom: var(--space-lg);
  letter-spacing: -0.03em;
}

.hero-subtitle {
  font-size: var(--text-xl);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-xl);
  line-height: 1.5;
}

.hero-description {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  max-width: 600px;
  margin: 0 auto var(--space-2xl);
  line-height: 1.6;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-md) var(--space-xl);
  font-size: var(--text-base);
  font-weight: 500;
  border-radius: var(--border-radius);
  border: 1px solid var(--color-border);
  background: var(--color-surface-elevated);
  color: var(--color-text);
  transition: all var(--transition-fast);
  cursor: pointer;
  text-decoration: none;
}

.btn:hover {
  background: var(--color-surface);
  border-color: var(--color-primary);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

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

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

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

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

.btn-disabled {
  opacity: 0.6;
  cursor: not-allowed;
  pointer-events: none;
  background: var(--color-surface) !important;
  color: var(--color-text-muted) !important;
  border-color: var(--color-border) !important;
}

.btn-disabled:hover {
  transform: none !important;
  box-shadow: none !important;
}

.btn-group {
  display: flex;
  gap: var(--space-md);
  flex-wrap: wrap;
  justify-content: center;
}

/* Cards */
.card {
  background: var(--color-surface-elevated);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius-lg);
  padding: var(--space-xl);
  transition: all var(--transition-base);
}

.card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.card-compact {
  padding: var(--space-lg);
}

/* Grid */
.grid {
  display: grid;
  gap: var(--space-lg);
}

.grid-2 {
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

.grid-3 {
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

/* Tags & Badges */
.tag {
  display: inline-flex;
  align-items: center;
  padding: var(--space-xs) var(--space-md);
  font-size: var(--text-sm);
  font-weight: 500;
  background: var(--color-surface);
  color: var(--color-text-secondary);
  border-radius: var(--border-radius);
  border: 1px solid var(--color-border);
  transition: all var(--transition-fast);
  margin: var(--space-xs) var(--space-xs) var(--space-xs) 0;
}

.tag:hover {
  background: var(--color-primary-light);
  border-color: var(--color-primary);
  color: var(--color-primary);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.tag-group {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xs);
  margin-top: var(--space-sm);
}

/* Stats */
.stat-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: var(--space-lg);
}

.stat {
  text-align: center;
}

.stat-value {
  font-size: var(--text-3xl);
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--space-xs);
}

.stat-label {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* Timeline */
.timeline {
  position: relative;
  padding-left: var(--space-xl);
}

.timeline::before {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--color-border);
}

.timeline-item {
  position: relative;
  padding-left: var(--space-xl);
  padding-bottom: var(--space-2xl);
}

.timeline-item::before {
  content: '';
  position: absolute;
  left: calc(-1 * var(--space-xl) - 5px);
  top: var(--space-md);
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--color-primary);
  border: 2px solid var(--color-bg);
}

.timeline-date {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-xs);
}

.timeline-title {
  font-size: var(--text-xl);
  font-weight: 600;
  margin-bottom: var(--space-xs);
}

.timeline-org {
  font-size: var(--text-base);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-md);
}

/* Sections */
.section {
  padding: var(--space-3xl) 0;
}

.section-header {
  text-align: center;
  max-width: 700px;
  margin: 0 auto var(--space-3xl);
}

.section-title {
  margin-bottom: var(--space-md);
}

.section-description {
  font-size: var(--text-lg);
  color: var(--color-text-secondary);
}

/* Footer */
footer {
  padding: var(--space-3xl) 0 var(--space-2xl);
  border-top: 1px solid var(--color-border);
  text-align: center;
  color: var(--color-text-muted);
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: var(--space-lg);
  margin-bottom: var(--space-lg);
}

.footer-links a {
  color: var(--color-text-secondary);
  font-size: var(--text-xl);
  transition: color var(--transition-fast);
}

.footer-links a:hover {
  color: var(--color-primary);
}

/* Utilities */
.text-center { text-align: center; }
.text-muted { color: var(--color-text-muted); }
.mt-sm { margin-top: var(--space-sm); }
.mt-md { margin-top: var(--space-md); }
.mt-lg { margin-top: var(--space-lg); }
.mt-xl { margin-top: var(--space-xl); }
.mb-sm { margin-bottom: var(--space-sm); }
.mb-md { margin-bottom: var(--space-md); }
.mb-lg { margin-bottom: var(--space-lg); }
.mb-xl { margin-bottom: var(--space-xl); }

/* Responsive */
@media (max-width: 768px) {
  .container {
    padding: 0 var(--space-md);
  }
  
  .nav-container {
    padding: var(--space-md) var(--space-lg);
    min-height: 60px;
    flex-wrap: wrap;
  }
  
  .brand {
    font-size: var(--text-lg);
  }
  
  .nav-links {
    gap: var(--space-sm);
    flex-wrap: wrap;
  }
  
  .nav-links a {
    font-size: var(--text-sm);
    padding: var(--space-xs) var(--space-sm);
    min-height: 40px;
  }
  
  .hero {
    padding: calc(80px + var(--space-xl)) 0 var(--space-xl);
  }
  
  .hero h1 {
    font-size: var(--text-3xl);
  }
  
  .hero-subtitle {
    font-size: var(--text-lg);
  }
  
  .hero-description {
    font-size: var(--text-base);
  }
  
  .btn-group {
    flex-direction: column;
    align-items: stretch;
  }
  
  .btn {
    justify-content: center;
    width: 100%;
  }
  
  .section {
    padding: var(--space-2xl) 0;
  }
  
  .section-title {
    font-size: var(--text-2xl);
  }
  
  h2 {
    font-size: var(--text-2xl);
  }
  
  h3 {
    font-size: var(--text-xl);
  }
  
  .card {
    padding: var(--space-lg);
  }
  
  .experience-item {
    padding: var(--space-lg);
  }
  
  .experience-content {
    grid-template-columns: 1fr;
  }
  
  .research-card-content {
    grid-template-columns: 1fr;
  }
  
  .coaching-role-content {
    grid-template-columns: 1fr;
  }
  
img {
  max-width: 100%;
  height: auto;
  display: block;
}
  
  .profile-img {
    width: 120px;
    height: 120px;
  }
  
  .hero-stats {
    grid-template-columns: 1fr;
  }
  
  .stat-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .impact-metrics {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 480px) {
  .nav-links {
    gap: var(--space-xs);
  }
  
  .nav-links a {
    font-size: 0.7rem;
  }
  
  .hero h1 {
    font-size: var(--text-2xl);
  }
  
  .stat-grid,
  .impact-metrics {
    grid-template-columns: 1fr;
  }
  
  .achievement-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* Animations */
@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

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

/* Print */
@media print {
  nav {
    position: static;
  }
  
  .btn {
    display: none;
  }
}