/* Base Styles */
:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --background-light: #ffffff;
    --text-light: #1f2937;
    --border-light: #e5e7eb;
    --card-bg-light: #f9fafb;
    --background-dark: #111827;
    --text-dark: #f3f4f6;
    --border-dark: #374151;
    --card-bg-dark: #1f2937;
  }
  
  * {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
  }
  
  body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
  }
  
  body.light {
    background-color: var(--background-light);
    color: var(--text-light);
  }
  
  body.dark {
    background-color: var(--background-dark);
    color: var(--text-dark);
  }
  
  /* Navigation */
  .navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    border-bottom: 1px solid var(--border-light);
  }
  
  .dark .navbar {
    border-color: var(--border-dark);
  }
  
  .nav-brand {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.25rem;
    font-weight: 600;
  }
  
  .nav-links {
    display: flex;
    gap: 2rem;
    align-items: center;
  }
  
  .nav-links a {
    text-decoration: none;
    color: inherit;
    position: relative;
  }
  
  .nav-links a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--primary-color);
    transition: width 0.3s;
  }
  
  .nav-links a:hover::after,
  .nav-links a.active::after {
    width: 100%;
  }
  
  .theme-toggle {
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
    color: inherit;
  }
  
  .theme-toggle .sun {
    display: none;
  }
  
  .dark .theme-toggle .sun {
    display: block;
  }
  
  .dark .theme-toggle .moon {
    display: none;
  }
  
  /* Pages */
  .page {
    display: none;
    padding: 2rem;
    max-width: 1200px;
    margin: 0 auto;
  }
  
  .page.active {
    display: block;
  }
  
  /* Home Page */
  .hero {
    text-align: center;
    padding: 4rem 1rem;
  }
  
  .hero h1 {
    font-size: 3rem;
    margin-bottom: 1rem;
  }
  
  .hero p {
    font-size: 1.25rem;
    margin-bottom: 2rem;
    color: #666;
  }
  
  .dark .hero p {
    color: #9ca3af;
  }
  
  .features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    padding: 2rem;
  }
  
  .feature-card {
    padding: 2rem;
    border-radius: 0.5rem;
    background-color: var(--card-bg-light);
    text-align: center;
    transition: transform 0.3s;
  }
  
  .dark .feature-card {
    background-color: var(--card-bg-dark);
  }
  
  .feature-card:hover {
    transform: translateY(-5px);
  }
  
  .feature-card svg {
    margin-bottom: 1rem;
    color: var(--primary-color);
  }
  
  /* Upload Page */
  .upload-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    padding: 2rem;
  }
  
  .upload-box {
    border: 2px dashed var(--border-light);
    border-radius: 0.5rem;
    padding: 2rem;
    text-align: center;
    transition: border-color 0.3s;
  }
  
  .dark .upload-box {
    border-color: var(--border-dark);
  }
  
  .upload-box.drag-over {
    border-color: var(--primary-color);
  }
  
  .file-input {
    display: none;
  }
  
  .file-label {
    display: inline-block;
    padding: 0.5rem 1rem;
    background-color: var(--primary-color);
    color: white;
    border-radius: 0.25rem;
    cursor: pointer;
    transition: background-color 0.3s;
  }
  
  .file-label:hover {
    background-color: var(--primary-hover);
  }
  
  .text-input-container {
    display: flex;
    flex-direction: column;
    gap: 1rem;
  }
  
  textarea {
    height: 200px;
    padding: 1rem;
    border: 1px solid var(--border-light);
    border-radius: 0.5rem;
    resize: vertical;
    background-color: var(--background-light);
    color: var(--text-light);
  }
  
  .dark textarea {
    background-color: var(--card-bg-dark);
    border-color: var(--border-dark);
    color: var(--text-dark);
  }
  
  /* Summary Page */
  .summary-container {
    background-color: var(--card-bg-light);
    border-radius: 0.5rem;
    padding: 2rem;
  }
  
  .dark .summary-container {
    background-color: var(--card-bg-dark);
  }
  
  .summary-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
  }
  
  .summary-actions {
    display: flex;
    gap: 1rem;
  }
  
  .action-button {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    border: 1px solid var(--border-light);
    border-radius: 0.25rem;
    background: none;
    color: inherit;
    cursor: pointer;
    transition: background-color 0.3s;
  }
  
  .dark .action-button {
    border-color: var(--border-dark);
  }
  
  .action-button:hover {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
  }
  
  .summary-content {
    display: grid;
    gap: 2rem;
  }
  
  .topics-list {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
  }
  
  .topic-tag {
    padding: 0.25rem 0.75rem;
    background-color: var(--primary-color);
    color: white;
    border-radius: 1rem;
    font-size: 0.875rem;
  }
  
  /* About Page */
  .process-steps {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin: 3rem 0;
  }
  
  .step {
    text-align: center;
    padding: 2rem;
    background-color: var(--card-bg-light);
    border-radius: 0.5rem;
  }
  
  .dark .step {
    background-color: var(--card-bg-dark);
  }
  
  .step-number {
    width: 40px;
    height: 40px;
    background-color: var(--primary-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 1rem;
    font-weight: bold;
  }
  
  /* Contact Page */
  .contact-form {
    max-width: 600px;
    margin: 0 auto;
  }
  
  .form-group {
    margin-bottom: 1.5rem;
  }
  
  .form-group label {
    display: block;
    margin-bottom: 0.5rem;
  }
  
  .form-group input,
  .form-group textarea {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-light);
    border-radius: 0.25rem;
    background-color: var(--background-light);
    color: var(--text-light);
  }
  
  .dark .form-group input,
  .dark .form-group textarea {
    background-color: var(--card-bg-dark);
    border-color: var(--border-dark);
    color: var(--text-dark);
  }
  
  /* Buttons */
  .cta-button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 0.25rem;
    cursor: pointer;
    font-weight: 500;
    transition: background-color 0.3s;
  }
  
  .cta-button:hover {
    background-color: var(--primary-hover);
  }
  
  /* Loading Animation */
  .loader {
    display: none;
    width: 20px;
    height: 20px;
    border: 2px solid #ffffff;
    border-radius: 50%;
    border-top-color: transparent;
    animation: spin 1s linear infinite;
    margin-left: 0.5rem;
  }
  
  @keyframes spin {
    to {
      transform: rotate(360deg);
    }
  }
  
  /* Responsive Design */
  @media (max-width: 768px) {
    .nav-links {
      gap: 1rem;
    }
  
    .hero h1 {
      font-size: 2rem;
    }
  
    .upload-container {
      grid-template-columns: 1fr;
    }
  
    .summary-header {
      flex-direction: column;
      gap: 1rem;
      text-align: center;
    }
  }