:root {
  /* Modern Primary Gradient Colors */
  --primary-color: #667eea;
  --primary-dark: #5a67d8;
  --primary-light: #818cf8;
  --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  
  /* Semantic Colors - Modern Palette */
  --success-color: #10b981;
  --success-light: #d1fae5;
  --success-dark: #059669;
  
  --danger-color: #ef4444;
  --danger-light: #fee2e2;
  --danger-dark: #dc2626;
  
  --warning-color: #f59e0b;
  --warning-light: #fef3c7;
  --warning-dark: #d97706;
  
  --info-color: #3b82f6;
  --info-light: #dbeafe;
  --info-dark: #2563eb;
  
  /* Purchase/Sale Theme Colors */
  --purchase-color: #3b82f6;
  --purchase-light: #eff6ff;
  --purchase-dark: #1e40af;
  
  --sale-color: #10b981;
  --sale-light: #ecfdf5;
  --sale-dark: #065f46;
  
  /* Neutral Colors */
  --dark-color: #1f2937;
  --text-primary: #111827;
  --text-secondary: #6b7280;
  --text-muted: #9ca3af;
  
  /* Background Colors */
  --light-bg: #f3f4f6;
  --white: #ffffff;
  --card-bg: #ffffff;
  
  /* Border Colors */
  --border-color: #e5e7eb;
  --border-light: #f3f4f6;
  
  /* Shadows - Modern depth */
  --shadow-xs: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.1), 0 1px 2px rgba(0,0,0,0.06);
  --shadow: 0 4px 6px rgba(0,0,0,0.07), 0 2px 4px rgba(0,0,0,0.06);
  --shadow-md: 0 6px 12px rgba(0,0,0,0.08), 0 3px 6px rgba(0,0,0,0.06);
  --shadow-lg: 0 10px 25px rgba(0,0,0,0.1), 0 6px 10px rgba(0,0,0,0.08);
  --shadow-xl: 0 20px 40px rgba(0,0,0,0.15);
  
  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition: 0.2s ease;
  --transition-slow: 0.3s ease;
  
  /* Border Radius */
  --radius-sm: 6px;
  --radius: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 20px;
  --radius-full: 9999px;
  
  /* Spacing */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 12px;
  --space-lg: 16px;
  --space-xl: 20px;
  --space-2xl: 24px;
  --space-3xl: 32px;
}

/* Dark Mode Variables */
body.dark-mode {
  --primary-color: #818cf8;
  --primary-dark: #667eea;
  --primary-light: #a5b4fc;
  --primary-gradient: linear-gradient(135deg, #818cf8 0%, #a78bfa 100%);
  
  --success-color: #34d399;
  --success-light: #064e3b;
  --success-dark: #10b981;
  
  --danger-color: #f87171;
  --danger-light: #7f1d1d;
  --danger-dark: #ef4444;
  
  --warning-color: #fbbf24;
  --warning-light: #78350f;
  --warning-dark: #f59e0b;
  
  --info-color: #60a5fa;
  --info-light: #1e3a5f;
  --info-dark: #3b82f6;
  
  --dark-color: #f3f4f6;
  --text-primary: #f9fafb;
  --text-secondary: #d1d5db;
  --text-muted: #9ca3af;
  
  --light-bg: #111827;
  --white: #1f2937;
  --card-bg: #1f2937;
  
  --border-color: #374151;
  --border-light: #1f2937;
  
  --shadow-xs: 0 1px 2px rgba(0,0,0,0.2);
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.3), 0 1px 2px rgba(0,0,0,0.2);
  --shadow: 0 4px 6px rgba(0,0,0,0.25), 0 2px 4px rgba(0,0,0,0.2);
  --shadow-md: 0 6px 12px rgba(0,0,0,0.3), 0 3px 6px rgba(0,0,0,0.25);
  --shadow-lg: 0 10px 25px rgba(0,0,0,0.35), 0 6px 10px rgba(0,0,0,0.3);
  --shadow-xl: 0 20px 40px rgba(0,0,0,0.45);
}

body.dark-mode {
  background: var(--light-bg);
  color: var(--text-primary);
}

body.dark-mode .tab,
body.dark-mode .item-card,
body.dark-mode .bill-item-row,
body.dark-mode .settings-card,
body.dark-mode .stock-item,
body.dark-mode .report-card,
body.dark-mode .date-filter-card,
body.dark-mode .popular-item,
body.dark-mode .item-report,
body.dark-mode .modern-card {
  background: var(--card-bg);
  color: var(--text-primary);
  border-color: var(--border-color);
}

body.dark-mode input,
body.dark-mode select,
body.dark-mode textarea {
  background: #374151;
  color: var(--text-primary);
  border-color: var(--border-color);
}

body.dark-mode input::placeholder {
  color: var(--text-muted);
}

body.dark-mode .top-bar {
  background: #1f2937;
  border-bottom-color: var(--border-color);
}

body.dark-mode .side-nav {
  background: #1f2937;
}

body.dark-mode .nav-menu a {
  color: var(--text-primary);
}

body.dark-mode .nav-menu a:hover {
  background: #374151;
}

body.dark-mode .nav-menu a.active {
  background: rgba(129, 140, 248, 0.15);
  color: var(--primary-color);
}

body.dark-mode .modal-box {
  background: #1f2937;
  color: var(--text-primary);
}

/* Global Base Styles */
* {
  box-sizing: border-box;
}

html {
  height: 100%;
  overflow: hidden;
  position: fixed;
  width: 100%;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: var(--light-bg);
  color: var(--text-primary);
  margin: 0;
  padding: 0;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  height: 100%;
  width: 100%;
  overflow: hidden;
  position: fixed;
  -webkit-overflow-scrolling: touch;
}

/* Modern Card Utility Class */
.modern-card {
  background: var(--card-bg);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
  border: 1px solid var(--border-color);
  padding: var(--space-lg);
  transition: box-shadow var(--transition), transform var(--transition);
}

.modern-card:hover {
  box-shadow: var(--shadow-md);
}

/* Modern Button Base */
.modern-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: var(--space-md) var(--space-lg);
  border-radius: var(--radius);
  font-size: 14px;
  font-weight: 600;
  border: none;
  cursor: pointer;
  transition: all var(--transition);
  text-decoration: none;
}

.modern-btn:active {
  transform: scale(0.98);
}

.modern-btn-primary {
  background: var(--primary-gradient);
  color: white;
  box-shadow: var(--shadow-sm);
}

.modern-btn-primary:hover {
  box-shadow: var(--shadow);
}

.modern-btn-success {
  background: linear-gradient(135deg, var(--success-color), var(--success-dark));
  color: white;
  box-shadow: var(--shadow-sm);
}

.modern-btn-danger {
  background: linear-gradient(135deg, var(--danger-color), var(--danger-dark));
  color: white;
  box-shadow: var(--shadow-sm);
}

.modern-btn-outline {
  background: transparent;
  color: var(--primary-color);
  border: 2px solid var(--primary-color);
}

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

/* Gradient Text Utility */
.gradient-text {
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

/* Status Badge Utilities */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 4px 10px;
  border-radius: var(--radius-full);
  font-size: 12px;
  font-weight: 600;
}

.badge-success {
  background: var(--success-light);
  color: var(--success-dark);
}

.badge-danger {
  background: var(--danger-light);
  color: var(--danger-dark);
}

.badge-warning {
  background: var(--warning-light);
  color: var(--warning-dark);
}

.badge-info {
  background: var(--info-light);
  color: var(--info-dark);
}