/* ===== CSS RESET & VARIABLES ===== */
:root {
  /* Color Palette - Professional Science Theme */
  --primary-color: #6366f1;
  --primary-dark: #4f46e5;
  --primary-light: #818cf8;
  --secondary-color: #06d6a0;
  --accent-color: #f59e0b;
  --danger-color: #ef4444;
  --success-color: #10b981;
  --warning-color: #f59e0b;
  --info-color: #3b82f6;
  
  /* Neutral Colors */
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-tertiary: #f1f5f9;
  --bg-card: #ffffff;
  --text-primary: #1e293b;
  --text-secondary: #64748b;
  --text-muted: #94a3b8;
  --text-light: #cbd5e1;
  --border-color: #e2e8f0;
  --border-light: #f1f5f9;
  
  /* Subject Colors */
  --physics-color: #3b82f6;
  --chemistry-color: #06d6a0;
  --mathematics-color: #8b5cf6;
  --engineering-color: #f59e0b;
  
  /* Gradients */
  --gradient-primary: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%);
  --gradient-physics: linear-gradient(135deg, #3b82f6 0%, #06b6d4 100%);
  --gradient-chemistry: linear-gradient(135deg, #06d6a0 0%, #10b981 100%);
  --gradient-math: linear-gradient(135deg, #8b5cf6 0%, #d946ef 100%);
  --gradient-hero: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  
  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  
  /* Border Radius */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 20px;
  --radius-full: 50%;
  
  /* Spacing */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;
  --space-3xl: 64px;
  
  /* Typography */
  --font-family: 'Inter', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;
  --font-size-4xl: 2.25rem;
  --font-size-5xl: 3rem;
  
  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;
  
  /* Z-index */
  --z-dropdown: 1000;
  --z-sticky: 1020;
  --z-fixed: 1030;
  --z-modal: 1040;
  --z-popover: 1050;
  --z-tooltip: 1060;
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-family);
  line-height: 1.6;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ===== LAYOUT & CONTAINER ===== */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-md);
}

@media (max-width: 480px) {
  .container {
    padding: 0 var(--space-sm);
  }
}

/* ===== HEADER & NAVIGATION ===== */
.header {
  background: var(--bg-primary);
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-light);
}

.nav-wrapper {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-md) 0;
  gap: var(--space-md);
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: var(--font-size-2xl);
  font-weight: 700;
  color: var(--primary-color);
  text-decoration: none;
}

.logo i {
  font-size: 1.75rem;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* Search Container */
.search-container {
  flex: 1;
  max-width: 500px;
  position: relative;
}

.search-box {
  display: flex;
  align-items: center;
  background: var(--bg-secondary);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-sm) var(--space-md);
  transition: all var(--transition-normal);
  position: relative;
}

.search-box:focus-within {
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
  background: var(--bg-primary);
}

.search-box i {
  color: var(--text-muted);
  margin-right: var(--space-sm);
}

.search-box input {
  flex: 1;
  border: none;
  outline: none;
  background: transparent;
  font-size: var(--font-size-base);
  color: var(--text-primary);
  font-family: var(--font-family);
}

.search-box input::placeholder {
  color: var(--text-muted);
}

.search-box button {
  background: var(--primary-color);
  border: none;
  border-radius: var(--radius-sm);
  color: white;
  padding: var(--space-xs) var(--space-sm);
  cursor: pointer;
  transition: background-color var(--transition-normal);
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 36px;
  min-height: 36px;
}

.search-box button:hover {
  background: var(--primary-dark);
}

/* Search Suggestions */
.search-suggestions {
  position: absolute;
  top: 100%;
  left: 0;
  right: 0;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  margin-top: var(--space-xs);
  display: none;
  z-index: var(--z-dropdown);
  max-height: 300px;
  overflow-y: auto;
}

.search-suggestions.show {
  display: block;
  animation: slideDown 0.2s ease;
}

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

.suggestion-item {
  padding: var(--space-md);
  cursor: pointer;
  border-bottom: 1px solid var(--border-light);
  transition: background-color var(--transition-fast);
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.suggestion-item:hover {
  background: var(--bg-secondary);
}

.suggestion-item:last-child {
  border-bottom: none;
}

.suggestion-item i {
  color: var(--text-muted);
  width: 16px;
}

/* Hamburger Menu */
.hamburger-menu {
  display: none;
  flex-direction: column;
  gap: 4px;
  cursor: pointer;
  padding: var(--space-sm);
  background: var(--bg-secondary);
  border-radius: var(--radius-sm);
  transition: background-color var(--transition-fast);
}

.hamburger-menu:hover {
  background: var(--bg-tertiary);
}

.hamburger-menu span {
  width: 24px;
  height: 3px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: all var(--transition-normal);
}

/* Mobile Menu */
.mobile-menu {
  position: fixed;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: var(--bg-primary);
  z-index: var(--z-modal);
  transition: left var(--transition-normal);
  overflow: hidden;
}

.mobile-menu.active {
  left: 0;
}

.mobile-menu-content {
  height: 100%;
  padding: var(--space-xl) var(--space-lg);
  overflow-y: auto;
  display: flex;
  flex-direction: column;
}

.mobile-menu-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-2xl);
  padding-bottom: var(--space-md);
  border-bottom: 1px solid var(--border-light);
}

.close-menu {
  background: none;
  border: none;
  font-size: var(--font-size-xl);
  color: var(--text-primary);
  cursor: pointer;
  padding: var(--space-xs);
  border-radius: var(--radius-sm);
  transition: background-color var(--transition-fast);
}

.close-menu:hover {
  background: var(--bg-secondary);
}

.mobile-nav {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  flex: 1;
}

.nav-item {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md);
  text-decoration: none;
  color: var(--text-primary);
  border-radius: var(--radius-md);
  transition: all var(--transition-normal);
  font-weight: 500;
}

.nav-item:hover,
.nav-item.active {
  background: var(--primary-color);
  color: white;
  transform: translateX(8px);
}

.nav-item i {
  width: 20px;
  text-align: center;
  font-size: var(--font-size-lg);
}

.mobile-footer {
  margin-top: auto;
  padding-top: var(--space-xl);
  border-top: 1px solid var(--border-light);
}

/* ===== MAIN CONTENT ===== */
.main-content {
  min-height: calc(100vh - 200px);
  padding-bottom: var(--space-2xl);
}

/* Hero Section */
.hero-section {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-2xl);
  align-items: center;
  padding: var(--space-2xl) 0;
  min-height: 80vh;
}

.hero-content {
  display: flex;
  flex-direction: column;
  gap: var(--space-xl);
}

.hero-title {
  font-size: var(--font-size-5xl);
  font-weight: 800;
  line-height: 1.1;
  color: var(--text-primary);
}

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

.hero-description {
  font-size: var(--font-size-xl);
  color: var(--text-secondary);
  line-height: 1.6;
}

.hero-buttons {
  display: flex;
  gap: var(--space-md);
  flex-wrap: wrap;
}

.hero-stats {
  display: flex;
  gap: var(--space-2xl);
  margin-top: var(--space-lg);
}

.stat {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.stat-number {
  font-size: var(--font-size-3xl);
  font-weight: 700;
  color: var(--primary-color);
  line-height: 1;
}

.stat-label {
  font-size: var(--font-size-sm);
  color: var(--text-secondary);
  margin-top: var(--space-xs);
}

.hero-graph {
  display: flex;
  justify-content: center;
  align-items: center;
}

.graph-preview-large {
  width: 100%;
  height: 400px;
  background: var(--bg-secondary);
  border-radius: var(--radius-xl);
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  border: 2px dashed var(--border-color);
  position: relative;
  overflow: hidden;
}

.loading-graph {
  text-align: center;
  color: var(--text-muted);
}

.loading-graph i {
  font-size: 3rem;
  margin-bottom: var(--space-md);
  color: var(--primary-color);
}

/* Ad Zone */
.ad-zone {
  margin: var(--space-2xl) 0;
}

.ad-container {
  width: 100%;
  background: var(--bg-secondary);
  border-radius: var(--radius-lg);
  border: 2px dashed var(--border-color);
  padding: var(--space-lg);
  text-align: center;
}

.ad-placeholder {
  color: var(--text-muted);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-sm);
}

.ad-placeholder i {
  font-size: 2rem;
  margin-bottom: var(--space-sm);
}

/* Subject Sections */
.subject-section {
  margin: var(--space-2xl) 0;
}

.section-header {
  text-align: center;
  margin-bottom: var(--space-2xl);
}

.subject-icon {
  width: 80px;
  height: 80px;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto var(--space-lg);
  font-size: 2rem;
  color: white;
}

.subject-section[data-subject="physics"] .subject-icon {
  background: var(--gradient-physics);
}

.subject-section[data-subject="chemistry"] .subject-icon {
  background: var(--gradient-chemistry);
}

.subject-section[data-subject="mathematics"] .subject-icon {
  background: var(--gradient-math);
}

.section-header h2 {
  font-size: var(--font-size-4xl);
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: var(--space-md);
}

.section-header p {
  font-size: var(--font-size-lg);
  color: var(--text-secondary);
  margin-bottom: var(--space-xl);
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

/* Category Filters */
.category-filters {
  display: flex;
  justify-content: center;
  gap: var(--space-sm);
  flex-wrap: wrap;
  margin-top: var(--space-lg);
}

.filter-btn {
  padding: var(--space-sm) var(--space-lg);
  border: 2px solid var(--border-color);
  background: var(--bg-primary);
  color: var(--text-secondary);
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: all var(--transition-normal);
  font-weight: 500;
  font-size: var(--font-size-sm);
}

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

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

/* ===== GRAPH CARDS & GRID ===== */
.graphs-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--space-lg);
  margin-bottom: var(--space-2xl);
}

.graph-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition-normal);
  cursor: pointer;
  display: flex;
  flex-direction: column;
}

.graph-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--primary-color);
}

.graph-preview {
  height: 200px;
  background: var(--bg-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
}

.graph-preview canvas,
.graph-preview img {
  max-width: 100%;
  max-height: 100%;
  object-fit: contain;
}

.graph-info {
  padding: var(--space-lg);
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.graph-info h3 {
  font-size: var(--font-size-lg);
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--space-xs);
  line-height: 1.3;
}

.graph-info p {
  color: var(--text-secondary);
  font-size: var(--font-size-sm);
  line-height: 1.5;
  flex: 1;
}

.graph-meta {
  display: flex;
  gap: var(--space-sm);
  flex-wrap: wrap;
  margin-top: var(--space-md);
}

.graph-tag {
  background: var(--bg-tertiary);
  color: var(--text-secondary);
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-full);
  font-size: var(--font-size-xs);
  font-weight: 500;
  text-transform: lowercase;
}

/* Graph Type Indicators */
.graph-type-badge {
  position: absolute;
  top: var(--space-sm);
  right: var(--space-sm);
  background: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(10px);
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-full);
  font-size: var(--font-size-xs);
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.graph-type-badge.interactive {
  color: var(--success-color);
}

.graph-type-badge.image {
  color: var(--info-color);
}

/* ===== BUTTONS ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-md) var(--space-lg);
  border: none;
  border-radius: var(--radius-md);
  font-size: var(--font-size-base);
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  transition: all var(--transition-normal);
  text-align: center;
  white-space: nowrap;
  font-family: var(--font-family);
  min-height: 44px;
  justify-content: center;
}

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

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

.btn-primary:hover {
  background: var(--primary-dark);
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn-secondary {
  background: var(--bg-secondary);
  color: var(--text-primary);
  border: 2px solid var(--border-color);
}

.btn-secondary:hover {
  background: var(--bg-tertiary);
  border-color: var(--primary-color);
  transform: translateY(-2px);
}

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

.btn-success:hover {
  background: #0da271;
  transform: translateY(-2px);
}

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

.btn-danger:hover {
  background: #dc2626;
  transform: translateY(-2px);
}

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

.btn-warning:hover {
  background: #d97706;
  transform: translateY(-2px);
}

/* ===== ABOUT SECTION ===== */
.about-section {
  margin: var(--space-2xl) 0;
}

.about-content {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--space-lg);
  margin-top: var(--space-2xl);
}

.about-card {
  background: var(--bg-card);
  padding: var(--space-2xl);
  border-radius: var(--radius-lg);
  text-align: center;
  border: 1px solid var(--border-light);
  transition: all var(--transition-normal);
}

.about-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: var(--primary-color);
}

.about-card i {
  font-size: 3rem;
  color: var(--primary-color);
  margin-bottom: var(--space-lg);
}

.about-card h3 {
  font-size: var(--font-size-xl);
  font-weight: 600;
  margin-bottom: var(--space-md);
  color: var(--text-primary);
}

.about-card p {
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ===== FOOTER ===== */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: var(--space-2xl) 0 var(--space-lg);
  margin-top: var(--space-2xl);
}

.footer-content {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: var(--space-2xl);
  margin-bottom: var(--space-2xl);
}

.footer-section h3,
.footer-section h4 {
  margin-bottom: var(--space-md);
  color: var(--text-primary);
}

.footer-section h3 {
  font-size: var(--font-size-xl);
  font-weight: 700;
}

.footer-section h4 {
  font-size: var(--font-size-lg);
  font-weight: 600;
}

.footer-section p,
.footer-section a {
  color: var(--text-secondary);
  text-decoration: none;
  margin-bottom: var(--space-sm);
  display: block;
  transition: color var(--transition-fast);
}

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

.footer-section i {
  width: 20px;
  margin-right: var(--space-sm);
  color: var(--text-muted);
}

.social-links {
  display: flex;
  gap: var(--space-md);
  margin-top: var(--space-md);
}

.social-link {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-full);
  color: var(--text-secondary);
  transition: all var(--transition-normal);
  text-decoration: none;
}

.social-link:hover {
  background: var(--primary-color);
  color: white;
  transform: translateY(-2px);
}

.footer-bottom {
  text-align: center;
  padding-top: var(--space-lg);
  border-top: 1px solid var(--border-color);
  color: var(--text-muted);
  font-size: var(--font-size-sm);
}

.footer-bottom i {
  color: var(--danger-color);
  margin: 0 var(--space-xs);
}

/* ===== MODAL STYLES ===== */
.modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.5);
  z-index: var(--z-modal);
  backdrop-filter: blur(5px);
  padding: var(--space-md);
  overflow-y: auto;
}

.modal.active {
  display: flex;
  align-items: center;
  justify-content: center;
  animation: fadeIn 0.3s ease;
}

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

.modal-content {
  background: var(--bg-primary);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-xl);
  width: 90%;
  max-width: 600px;
  max-height: 90vh;
  overflow-y: auto;
  animation: scaleIn 0.3s ease;
}

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

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-lg);
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  background: var(--bg-primary);
  border-radius: var(--radius-xl) var(--radius-xl) 0 0;
  z-index: 1;
}

.modal-header h3 {
  color: var(--text-primary);
  font-size: var(--font-size-xl);
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.close-modal {
  background: none;
  border: none;
  font-size: var(--font-size-lg);
  color: var(--text-muted);
  cursor: pointer;
  padding: var(--space-xs);
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 32px;
  min-height: 32px;
}

.close-modal:hover {
  background: var(--bg-secondary);
  color: var(--text-primary);
}

.modal-body {
  padding: var(--space-lg);
}

/* ===== ADMIN PANEL STYLES ===== */
.admin-modal {
  max-width: 800px;
}

.admin-tabs {
  display: flex;
  border-bottom: 1px solid var(--border-color);
  margin-bottom: var(--space-lg);
  gap: var(--space-sm);
}

.tab-btn {
  background: none;
  border: none;
  padding: var(--space-md) var(--space-lg);
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
  border-bottom: 2px solid transparent;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  white-space: nowrap;
}

.tab-btn:hover {
  color: var(--primary-color);
}

.tab-btn.active {
  color: var(--primary-color);
  border-bottom-color: var(--primary-color);
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
  animation: fadeIn 0.3s ease;
}

.admin-section {
  margin-bottom: var(--space-2xl);
}

.admin-section h4 {
  font-size: var(--font-size-lg);
  font-weight: 600;
  margin-bottom: var(--space-lg);
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

/* Upload Type Selector */
.upload-type-selector {
  display: flex;
  gap: var(--space-sm);
  margin-bottom: var(--space-lg);
  flex-wrap: wrap;
}

.type-btn {
  flex: 1;
  min-width: 120px;
  padding: var(--space-lg);
  border: 2px solid var(--border-color);
  background: var(--bg-secondary);
  color: var(--text-secondary);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-normal);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-sm);
  font-weight: 500;
}

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

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

.type-btn i {
  font-size: 1.5rem;
}

/* Graph Form */
.graph-form {
  display: flex;
  flex-direction: column;
  gap: var(--space-lg);
}

.form-section {
  display: block;
}

.form-section.hidden {
  display: none;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-md);
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.form-group label {
  font-weight: 500;
  color: var(--text-primary);
  font-size: var(--font-size-sm);
}

.form-group input,
.form-group select,
.form-group textarea {
  padding: var(--space-md);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  font-size: var(--font-size-base);
  font-family: var(--font-family);
  transition: border-color var(--transition-fast);
  background: var(--bg-primary);
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--primary-color);
}

.form-group textarea {
  resize: vertical;
  min-height: 80px;
}

/* Code Editor */
#graphCode {
  font-family: 'Courier New', monospace;
  font-size: var(--font-size-sm);
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
}

.code-actions {
  display: flex;
  gap: var(--space-sm);
  margin-top: var(--space-sm);
}

.code-preview {
  margin-top: var(--space-md);
  padding: var(--space-md);
  background: var(--bg-secondary);
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  min-height: 100px;
  display: none;
}

.code-preview:not(:empty) {
  display: block;
}

/* Image Upload */
.image-upload-zone {
  border: 2px dashed var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-2xl);
  text-align: center;
  cursor: pointer;
  transition: all var(--transition-normal);
  background: var(--bg-secondary);
}

.image-upload-zone:hover {
  border-color: var(--primary-color);
  background: var(--bg-tertiary);
}

.image-upload-zone.dragover {
  border-color: var(--primary-color);
  background: var(--primary-light);
  color: white;
}

.image-upload-zone i {
  font-size: 3rem;
  color: var(--text-muted);
  margin-bottom: var(--space-md);
}

.image-preview {
  margin-top: var(--space-md);
  display: none;
}

.image-preview:not(:empty) {
  display: block;
}

.image-preview img {
  max-width: 100%;
  max-height: 200px;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
}

.form-actions {
  display: flex;
  gap: var(--space-md);
  justify-content: flex-end;
  margin-top: var(--space-lg);
  padding-top: var(--space-lg);
  border-top: 1px solid var(--border-color);
}

/* Admin Graphs List */
.admin-graphs-list {
  max-height: 400px;
  overflow-y: auto;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
}

.admin-graph-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--space-md);
  border-bottom: 1px solid var(--border-light);
  transition: background-color var(--transition-fast);
}

.admin-graph-item:hover {
  background: var(--bg-secondary);
}

.admin-graph-item:last-child {
  border-bottom: none;
}

.graph-item-info h5 {
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--space-xs);
}

.graph-item-meta {
  display: flex;
  gap: var(--space-md);
  font-size: var(--font-size-sm);
  color: var(--text-muted);
}

.graph-item-actions {
  display: flex;
  gap: var(--space-sm);
}

/* Ad Management */
.ad-zones-management {
  display: flex;
  flex-direction: column;
  gap: var(--space-xl);
}

.ad-zone-config {
  background: var(--bg-secondary);
  padding: var(--space-lg);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-color);
}

.ad-zone-config h5 {
  font-weight: 600;
  margin-bottom: var(--space-md);
  color: var(--text-primary);
}

.ad-upload-area {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.ad-preview {
  min-height: 100px;
  border: 2px dashed var(--border-color);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-primary);
}

.ad-preview:not(:empty) {
  border-style: solid;
}

.ad-preview img {
  max-width: 100%;
  max-height: 150px;
  border-radius: var(--radius-sm);
}

.ad-upload-actions {
  display: flex;
  gap: var(--space-sm);
  flex-wrap: wrap;
}

/* Settings */
.setting-group {
  margin-bottom: var(--space-xl);
}

.setting-group label {
  display: block;
  font-weight: 500;
  margin-bottom: var(--space-md);
  color: var(--text-primary);
}

.password-change {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.data-actions {
  display: flex;
  gap: var(--space-md);
  flex-wrap: wrap;
}

/* ===== GRAPH DETAIL MODAL ===== */
.graph-detail-modal {
  max-width: 900px;
}

.graph-detail-content {
  padding: var(--space-lg);
}

.graph-detail-preview {
  width: 100%;
  height: 300px;
  background: var(--bg-secondary);
  border-radius: var(--radius-lg);
  margin-bottom: var(--space-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--border-color);
}

.graph-detail-info {
  display: grid;
  grid-template-columns: 2fr 1fr;
  gap: var(--space-2xl);
}

.graph-detail-main h3 {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  margin-bottom: var(--space-md);
  color: var(--text-primary);
}

.graph-equation {
  font-size: var(--font-size-xl);
  font-family: 'Courier New', monospace;
  background: var(--bg-tertiary);
  padding: var(--space-md);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-lg);
  border-left: 4px solid var(--primary-color);
}

.graph-description {
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: var(--space-lg);
}

.graph-detail-sidebar {
  background: var(--bg-secondary);
  padding: var(--space-lg);
  border-radius: var(--radius-lg);
  height: fit-content;
}

.sidebar-section {
  margin-bottom: var(--space-lg);
}

.sidebar-section:last-child {
  margin-bottom: 0;
}

.sidebar-section h4 {
  font-size: var(--font-size-base);
  font-weight: 600;
  margin-bottom: var(--space-sm);
  color: var(--text-primary);
}

/* ===== LOADING & UTILITY CLASSES ===== */
.loading-spinner {
  width: 40px;
  height: 40px;
  border: 4px solid var(--border-color);
  border-left: 4px solid var(--primary-color);
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}

.hidden {
  display: none !important;
}

.text-center {
  text-align: center;
}

.text-left {
  text-align: left;
}

.text-right {
  text-align: right;
}

.fade-in {
  animation: fadeIn 0.5s ease-in;
}

.slide-in {
  animation: slideIn 0.3s ease-out;
}

@keyframes slideIn {
  from { transform: translateX(-100%); }
  to { transform: translateX(0); }
}

/* ===== RESPONSIVE DESIGN ===== */
@media (max-width: 1024px) {
  .hero-section {
    grid-template-columns: 1fr;
    text-align: center;
    gap: var(--space-xl);
  }
  
  .hero-stats {
    justify-content: center;
  }
  
  .footer-content {
    grid-template-columns: 1fr 1fr;
    gap: var(--space-xl);
  }
  
  .graph-detail-info {
    grid-template-columns: 1fr;
    gap: var(--space-lg);
  }
}

@media (max-width: 768px) {
  .search-container {
    display: none;
  }
  
  .hamburger-menu {
    display: flex;
  }
  
  .nav-wrapper {
    padding: var(--space-sm) 0;
  }
  
  .hero-title {
    font-size: var(--font-size-4xl);
  }
  
  .graphs-grid {
    grid-template-columns: 1fr;
  }
  
  .form-row {
    grid-template-columns: 1fr;
  }
  
  .admin-tabs {
    flex-direction: column;
  }
  
  .tab-btn {
    justify-content: center;
  }
  
  .upload-type-selector {
    flex-direction: column;
  }
  
  .hero-buttons {
    flex-direction: column;
  }
  
  .btn {
    width: 100%;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 var(--space-sm);
  }
  
  .hero-title {
    font-size: var(--font-size-3xl);
  }
  
  .section-header h2 {
    font-size: var(--font-size-2xl);
  }
  
  .footer-content {
    grid-template-columns: 1fr;
    gap: var(--space-xl);
  }
  
  .category-filters {
    justify-content: flex-start;
    overflow-x: auto;
    padding-bottom: var(--space-sm);
  }
  
  .filter-btn {
    white-space: nowrap;
  }
  
  .modal-content {
    width: 95%;
    margin: var(--space-sm);
  }
  
  .form-actions {
    flex-direction: column;
  }
  
  .hero-stats {
    flex-direction: column;
    gap: var(--space-lg);
  }
}

/* ===== ACCESSIBILITY ===== */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

@media (prefers-contrast: high) {
  :root {
    --border-color: #000000;
    --text-secondary: #000000;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.8);
  }
}

/* Focus styles for keyboard navigation */
button:focus-visible,
input:focus-visible,
a:focus-visible,
select:focus-visible,
textarea:focus-visible {
  outline: 2px solid var(--primary-color);
  outline-offset: 2px;
}

/* Skip to main content for screen readers */
.skip-to-content {
  position: absolute;
  top: -40px;
  left: 0;
  background: var(--primary-color);
  color: white;
  padding: var(--space-sm);
  text-decoration: none;
  z-index: var(--z-tooltip);
  border-radius: 0 0 var(--radius-md) 0;
}

.skip-to-content:focus {
  top: 0;
}

/* ===== PRINT STYLES ===== */
@media print {
  .header,
  .footer,
  .ad-zone,
  .mobile-menu,
  .admin-panel {
    display: none !important;
  }
  
  .main-content {
    margin: 0;
    padding: 0;
  }
  
  .graph-card {
    break-inside: avoid;
    box-shadow: none;
    border: 1px solid #000;
  }
}