:root {
  --primary: #bd5d38;
  --primary-dark: #a0522d;
  --text-muted: #6c757d;
  --success: #28a745;
  --warning: #ffc107;
  --light: #f8f9fa;
  --shadow: 0 0.125rem 0.25rem rgba(0, 0, 0, 0.075);
  --shadow-hover: 0 0.5rem 1rem rgba(0, 0, 0, 0.15);
  --border-radius: 0.5rem;
  --transition: all 0.3s ease;
}

* {
  box-sizing: border-box;
}

body {
  font-family: 'Muli', system-ui, sans-serif;
  line-height: 1.6;
  color: #333;
}

/* Accessibility */
.skip-to-main-content-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 999;
  padding: 0.5rem 1rem;
  background: #fff;
  color: #000;
  text-decoration: none;
  border: 1px solid #000;
}

.skip-to-main-content-link:focus {
  left: 0;
}

/* Navigation */
.navbar {
  backdrop-filter: blur(10px);
  background: rgba(255, 255, 255, 0.95) !important;
  transition: var(--transition);
}

.navbar-brand {
  font-family: 'Saira Extra Condensed', sans-serif;
  font-weight: 700;
  color: var(--primary) !important;
}

.nav-link {
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.05rem;
  transition: var(--transition);
}

.nav-link:hover,
.nav-link:focus {
  color: var(--primary) !important;
}

/* Hero */
.hero-section {
  min-height: 100vh;
  display: flex;
  align-items: center;
}

.hero-content h1 {
  font-family: 'Saira Extra Condensed', sans-serif;
  font-weight: 700;
  line-height: 1.1;
}

.hero-content h2 {
  color: var(--text-muted);
}

.hero-content h1 small {
  font-size: 0.6em;
  font-weight: 400;
}

/* Social & Links */
.social-link {
  color: var(--text-muted);
  text-decoration: none;
  transition: var(--transition);
  display: inline-block;
}

.social-link:hover {
  color: var(--primary);
  transform: translateY(-2px);
  text-decoration: none;
}

.hero-image img {
  transition: var(--transition);
}

.hero-image img:hover {
  transform: scale(1.05);
}

/* Cards & Publications */
.card {
  border: none;
  box-shadow: var(--shadow);
  transition: var(--transition);
  border-radius: var(--border-radius);
}

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

.border-primary {
  border-left: 4px solid var(--primary) !important;
}

.text-success {
  color: var(--success) !important;
}

.text-warning {
  color: var(--warning) !important;
}

/* Buttons */
.btn {
  border-radius: var(--border-radius);
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.05rem;
  transition: var(--transition);
}

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

.btn-primary:hover,
.btn-outline-primary:hover {
  background: var(--primary-dark);
  border-color: var(--primary-dark);
  transform: translateY(-1px);
}

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

/* Publication Lists */
.ml-papers .fa-circle,
.physics-papers .fa-circle {
  margin: 0.5rem 0.75rem 0 0 !important;
}

/* Remove scroll animations for better performance and user preference */

@keyframes slideInRight {
  from { transform: translateX(100%); opacity: 0; }
  to { transform: translateX(0); opacity: 1; }
}

@keyframes slideOutRight {
  from { transform: translateX(0); opacity: 1; }
  to { transform: translateX(100%); opacity: 0; }
}

/* States */
.navbar-shrink {
  background: rgba(255, 255, 255, 0.98) !important;
  backdrop-filter: blur(10px);
}

/* Focus Accessibility */
.btn:focus,
.nav-link:focus {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

/* Enhanced Responsive Design */
@media (max-width: 991.98px) {
  .hero-section {
    min-height: auto;
    padding: 2rem 0;
  }
  
  .hero-image {
    margin-top: 2rem;
    text-align: center !important;
  }
  
  .d-none.d-lg-block {
    display: block !important;
    margin-top: 2rem;
  }
}

@media (max-width: 768px) {
  .display-4 {
    font-size: 2.25rem;
  }
  
  .social-link {
    font-size: 1.75rem;
    margin-right: 0.75rem;
  }
  
  .card {
    margin-bottom: 1rem;
  }
  
  .btn-group {
    flex-wrap: wrap;
    gap: 0.25rem;
  }
  
  .navbar-nav {
    text-align: center;
  }
  
  .hero-content {
    text-align: center;
  }
}

@media (max-width: 576px) {
  .display-4 {
    font-size: 1.75rem;
  }
  
  .btn-group-sm .btn {
    padding: 0.2rem 0.4rem;
    font-size: 0.7rem;
    margin-bottom: 0.25rem;
  }
  
  .card-body {
    padding: 0.75rem;
  }
  
  .social-link {
    font-size: 1.5rem;
    margin-right: 0.5rem;
  }
  
  .container {
    padding-left: 0.75rem;
    padding-right: 0.75rem;
  }
  
  .list-unstyled li {
    margin-bottom: 1rem;
  }
  
  h6 {
    font-size: 0.9rem;
    line-height: 1.3;
  }
}

@media (max-width: 380px) {
  .btn-group-sm .btn {
    font-size: 0.6rem;
    padding: 0.15rem 0.3rem;
  }
  
  .display-4 {
    font-size: 1.5rem;
  }
  
  .social-link {
    font-size: 1.25rem;
  }
}

/* Print */
@media print {
  .navbar, .btn, footer { display: none !important; }
  .hero-section { min-height: auto; }
  body { font-size: 12pt; line-height: 1.4; }
}