/* RRB Electronics Learning Platform - Main Styles */

/* CSS Custom Properties (Variables) */
:root {
  /* Colors */
  --primary-color: #4a90e2;
  --primary-dark: #357abd;
  --primary-light: #6ba3e8;
  --secondary-color: #7b68ee;
  --accent-color: #ff6b6b;
  --success-color: #51cf66;
  --warning-color: #ffd43b;
  --danger-color: #ff6b6b;
  --info-color: #74c0fc;
  
  /* Text Colors */
  --text-primary: #2c3e50;
  --text-secondary: #5a6c7d;
  --text-muted: #8e9aa6;
  --text-light: #ffffff;
  
  /* Enhanced contrast for better readability */
  --text-high-contrast: #1a252f;
  --text-medium-contrast: #495461;
  
  /* Background Colors */
  --bg-primary: #ffffff;
  --bg-secondary: #f8f9fa;
  --bg-dark: #343a40;
  --bg-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --bg-gradient-alt: linear-gradient(135deg, #4a90e2 0%, #7b68ee 100%);
  
  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 3rem;
  --spacing-xxl: 4rem;

/* Enhanced spacing for desktop */
@media (min-width: 1200px) {
  :root {
    --spacing-xs: 0.3rem;
    --spacing-sm: 0.6rem;
    --spacing-md: 1.2rem;
    --spacing-lg: 1.8rem;
    --spacing-xl: 3.5rem;
    --spacing-xxl: 5rem;
  }
}
  
  /* Typography */
  --font-family-base: 'Segoe UI', 'Roboto', 'Helvetica Neue', Arial, sans-serif;
  --font-family-mono: 'SF Mono', Monaco, 'Cascadia Code', 'Courier New', monospace;
  --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;

/* Enhanced typography for desktop */
@media (min-width: 1200px) {
  :root {
    --font-size-xs: 0.8rem;
    --font-size-sm: 0.95rem;
    --font-size-base: 1.1rem;
    --font-size-lg: 1.25rem;
    --font-size-xl: 1.4rem;
    --font-size-2xl: 1.75rem;
    --font-size-3xl: 2.1rem;
    --font-size-4xl: 2.5rem;
  }
}
  
  /* 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 */
  --border-radius-sm: 0.25rem;
  --border-radius-md: 0.5rem;
  --border-radius-lg: 0.75rem;
  --border-radius-xl: 1rem;
  --border-radius-full: 9999px;
  
  /* Transitions */
  --transition-fast: 0.15s ease-in-out;
  --transition-base: 0.25s ease-in-out;
  --transition-slow: 0.3s ease-in-out;
  
  /* Z-index */
  --z-dropdown: 1000;
  --z-sticky: 1020;
  --z-fixed: 1030;
  --z-modal-backdrop: 1040;
  --z-modal: 1050;
  --z-popover: 1060;
  --z-tooltip: 1070;
}

/* Dark Theme Variables */
[data-theme="dark"] {
  --text-primary: #ffffff;
  --text-secondary: #adb5bd;
  --text-muted: #6c757d;
  --bg-primary: #1a1a1a;
  --bg-secondary: #2d2d2d;
  --bg-dark: #000000;
  --shadow-md: 0 4px 6px -1px rgba(255, 255, 255, 0.1), 0 2px 4px -1px rgba(255, 255, 255, 0.06);
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

body {
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  line-height: 1.6;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  transition: background-color var(--transition-base), color var(--transition-base);
  /* Performance optimization */
  -webkit-transform: translateZ(0);
  transform: translateZ(0);
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.2;
  margin-bottom: var(--spacing-md);
}

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

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

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

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

/* Main App Container */
.app-container {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Header Styles */
.main-header {
  background: var(--bg-primary);
  border-bottom: 1px solid #e9ecef;
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: 0;
  z-index: var(--z-sticky);
  transition: background-color var(--transition-base);
}

.header-content {
  max-width: 1600px;
  margin: 0 auto;
  padding: var(--spacing-md) var(--spacing-lg);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--spacing-md);
}

.logo-section {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

.logo {
  width: 48px;
  height: 48px;
  border-radius: var(--border-radius-md);
}

.logo-section h1 {
  font-size: var(--font-size-xl);
  color: var(--primary-color);
  margin: 0;
}

.subtitle {
  font-size: var(--font-size-sm);
  color: var(--text-muted);
  margin: 0;
}

/* Navigation */
.main-nav {
  display: flex;
  align-items: center;
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  font-size: var(--font-size-xl);
  cursor: pointer;
  padding: var(--spacing-sm);
  border-radius: var(--border-radius-md);
  transition: background-color var(--transition-fast);
}

.nav-toggle:hover {
  background-color: var(--bg-secondary);
}

.nav-links {
  display: flex;
  list-style: none;
  gap: var(--spacing-lg);
  margin: 0;
  padding: 0;
}

/* Enhanced navigation for desktop */
@media (min-width: 992px) {
  .nav-links {
    gap: var(--spacing-xl);
  }
  
  .nav-link {
    position: relative;
    padding: var(--spacing-md) var(--spacing-lg);
    font-size: var(--font-size-lg);
  }
  
  .nav-link::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 50%;
    width: 0;
    height: 3px;
    background: var(--primary-color);
    transition: all var(--transition-base);
    transform: translateX(-50%);
  }
  
  .nav-link:hover::after,
  .nav-link.active::after {
    width: 80%;
  }
}

.nav-link {
  color: var(--text-primary);
  font-weight: 500;
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--border-radius-md);
  transition: all var(--transition-fast);
  text-decoration: none;
}

.nav-link:hover,
.nav-link.active {
  background-color: var(--primary-color);
  color: var(--text-light);
  text-decoration: none;
}

/* Header Actions */
.header-actions {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

.theme-toggle,
.install-app {
  background: none;
  border: 2px solid var(--primary-color);
  color: var(--primary-color);
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--border-radius-md);
  cursor: pointer;
  font-weight: 500;
  transition: all var(--transition-fast);
}

.theme-toggle:hover,
.install-app:hover {
  background-color: var(--primary-color);
  color: var(--text-light);
}

/* Hero Section */
.hero-section {
  background: var(--bg-gradient);
  color: var(--text-light);
  padding: var(--spacing-xxl) var(--spacing-lg);
  text-align: center;
}

.hero-content {
  max-width: 1000px;
  margin: 0 auto;
}

.hero-content h2 {
  font-size: var(--font-size-4xl);
  margin-bottom: var(--spacing-lg);
  font-weight: 700;
}

.hero-content p {
  font-size: var(--font-size-lg);
  margin-bottom: var(--spacing-xl);
  color: rgba(255, 255, 255, 0.9);
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: var(--spacing-xl);
  margin-bottom: var(--spacing-xl);
  flex-wrap: wrap;
}

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

.stat-number {
  display: block;
  font-size: var(--font-size-3xl);
  font-weight: 700;
  color: var(--text-light);
}

.stat-label {
  font-size: var(--font-size-sm);
  color: rgba(255, 255, 255, 0.8);
}

.hero-actions {
  display: flex;
  justify-content: center;
  gap: var(--spacing-lg);
  flex-wrap: wrap;
}

/* CTA Buttons */
.cta-button {
  padding: var(--spacing-md) var(--spacing-xl);
  border: none;
  border-radius: var(--border-radius-lg);
  font-size: var(--font-size-lg);
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-base);
  text-decoration: none;
  display: inline-block;
  text-align: center;
  min-width: 160px;
}

.cta-button.primary {
  background-color: var(--text-light);
  color: var(--primary-color);
  box-shadow: var(--shadow-lg);
}

.cta-button.primary:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-xl);
}

.cta-button.secondary {
  background-color: transparent;
  color: var(--text-light);
  border: 2px solid var(--text-light);
}

.cta-button.secondary:hover {
  background-color: var(--text-light);
  color: var(--primary-color);
}

/* Section Headers */
.section-header {
  text-align: center;
  margin-bottom: var(--spacing-xl);
  padding: 0 var(--spacing-lg);
}

.section-header h2 {
  font-size: var(--font-size-3xl);
  color: var(--text-primary);
  margin-bottom: var(--spacing-md);
}

.section-header p {
  font-size: var(--font-size-lg);
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto;
}

/* Common Section Styles */
section {
  padding: var(--spacing-xxl) var(--spacing-lg);
  max-width: 1400px;
  margin: 0 auto;
}

/* Enhanced desktop optimization */
@media (min-width: 1200px) {
  section {
    max-width: 1600px;
    padding: var(--spacing-xxl) var(--spacing-xl);
  }
  
  /* Better text contrast and readability on desktop */
  .module-card h3 {
    color: var(--text-high-contrast);
  }
  
  .module-card p {
    color: var(--text-medium-contrast);
  }
  
  /* Improved card spacing and hover effects */
  .module-card {
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  }
  
  .module-card:hover {
    transform: translateY(-8px) scale(1.02);
    box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
  }
}

/* Grid Layouts */
.modules-grid,
.tools-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: var(--spacing-xl);
  margin-top: var(--spacing-xl);
  /* Better alignment for grid items */
  align-items: stretch;
}

/* Enhanced grid for larger screens */
@media (min-width: 1200px) {
  .modules-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-xl);
    /* Improved minimum card width for desktop */
    grid-template-columns: repeat(auto-fit, minmax(380px, 1fr));
  }
  
  .tools-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-xl);
  }
}

@media (min-width: 1600px) {
  .modules-grid {
    grid-template-columns: repeat(4, 1fr);
    gap: var(--spacing-xxl);
    /* Maximum 4 columns on very large screens */
    grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    max-width: 1800px;
    margin-left: auto;
    margin-right: auto;
  }
  
  .tools-grid {
    grid-template-columns: repeat(4, 1fr);
    gap: var(--spacing-xxl);
  }
}

.quick-access-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: var(--spacing-lg);
  max-width: 600px;
  margin: var(--spacing-xl) auto 0;
}

/* Loading States */
.loading-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.8);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: var(--z-modal);
}

.loading-spinner {
  text-align: center;
  color: var(--text-light);
}

.spinner {
  width: 50px;
  height: 50px;
  border: 4px solid rgba(255, 255, 255, 0.3);
  border-top: 4px solid var(--text-light);
  border-radius: 50%;
  animation: spin 1s linear infinite;
  margin: 0 auto var(--spacing-md);
}

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

/* Footer */
.main-footer {
  background-color: var(--bg-dark);
  color: var(--text-light);
  margin-top: auto;
}

.footer-content {
  max-width: 1600px;
  margin: 0 auto;
  padding: var(--spacing-xl) var(--spacing-lg);
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-xl);
}

.footer-section h4 {
  color: var(--text-light);
  margin-bottom: var(--spacing-md);
  font-size: var(--font-size-lg);
}

.footer-section ul {
  list-style: none;
  padding: 0;
}

.footer-section ul li {
  margin-bottom: var(--spacing-sm);
}

.footer-section ul li a {
  color: rgba(255, 255, 255, 0.8);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.footer-section ul li a:hover {
  color: var(--text-light);
  text-decoration: none;
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.2);
  padding: var(--spacing-lg);
  text-align: center;
  color: rgba(255, 255, 255, 0.7);
}

.footer-bottom p {
  margin: 0;
  font-size: var(--font-size-sm);
}

/* Utility Classes */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.d-none { display: none; }
.d-block { display: block; }
.d-flex { display: flex; }
.d-grid { display: grid; }

.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.align-center { align-items: center; }

.mb-0 { margin-bottom: 0; }
.mb-1 { margin-bottom: var(--spacing-xs); }
.mb-2 { margin-bottom: var(--spacing-sm); }
.mb-3 { margin-bottom: var(--spacing-md); }
.mb-4 { margin-bottom: var(--spacing-lg); }
.mb-5 { margin-bottom: var(--spacing-xl); }

.mt-0 { margin-top: 0; }
.mt-1 { margin-top: var(--spacing-xs); }
.mt-2 { margin-top: var(--spacing-sm); }
.mt-3 { margin-top: var(--spacing-md); }
.mt-4 { margin-top: var(--spacing-lg); }
.mt-5 { margin-top: var(--spacing-xl); }

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

/* Enhanced focus for interactive cards on desktop */
@media (min-width: 992px) {
  .module-card:focus-within,
  .tool-card:focus-within {
    outline: 3px solid var(--primary-color);
    outline-offset: 4px;
  }
}

/* High Contrast Mode Support */
@media (prefers-contrast: high) {
  :root {
    --primary-color: #0066cc;
    --text-primary: #000000;
    --text-secondary: #333333;
    --bg-primary: #ffffff;
    --bg-secondary: #f5f5f5;
  }
}

/* Reduced Motion Support */
@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  
  html {
    scroll-behavior: auto;
  }
}