:root {
   --primary: #2563eb;
   --secondary: #0891b2;
   --dark: #1e293b;
   --light: #f8fafc;
   --accent: #8b5cf6;
   --success: #10b981;
   --danger: #ef4444;
   --warning: #f59e0b;
   --info: #0ea5e9;
   }

   * {
   margin: 0;
   padding: 0;
   box-sizing: border-box;
   font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
   }

   body {
   background-color: #f0f4f8;
   }

   .container {
   width: 90%;
   max-width: 1200px;
   margin: 0 auto;
   padding: 0 15px;
   }

   /* Header Styles */
   header {
   background-color: white;
   box-shadow: 0 2px 15px rgba(0, 0, 0, 0.1);
   position: fixed;
   width: 100%;
   top: 0;
   z-index: 100;
   }

   .navbar {
   display: flex;
   justify-content: space-between;
   align-items: center;
   padding: 15px 0;
   }

   .logo {
   display: flex;
   align-items: center;
   }

   .logo img {
   height: 40px;
   margin-right: 10px;
   }

   .logo h1 {
   font-size: 1.5rem;
   color: var(--primary);
   font-weight: 700;
   }

   .logo span {
   color: var(--secondary);
   }

   .nav-links {
   display: flex;
   list-style: none;
   }

   .nav-links li {
   margin-left: 30px;
   }

   .nav-links a {
   text-decoration: none;
   color: var(--dark);
   font-weight: 600;
   transition: color 0.3s ease;
   }

   .nav-links a:hover {
   color: var(--primary);
   }

   .menu-toggle {
   display: none;
   flex-direction: column;
   cursor: pointer;
   }

   .menu-toggle span {
   height: 3px;
   width: 25px;
   background-color: var(--dark);
   margin: 2px 0;
   border-radius: 2px;
   transition: all 0.3s ease;
   }

   /* Hero Section */
   .hero {
   background: linear-gradient(135deg, var(--primary), var(--secondary));
   color: white;
   padding: 150px 0 100px;
   text-align: center;
   position: relative;
   overflow: hidden;
   }

   .hero-content {
   position: relative;
   z-index: 2;
   }

   .hero h1 {
   font-size: 3rem;
   margin-bottom: 20px;
   font-weight: 800;
   }

   .hero p {
   font-size: 1.2rem;
   margin-bottom: 40px;
   max-width: 800px;
   margin-left: auto;
   margin-right: auto;
   }

   .cta-buttons {
   display: flex;
   justify-content: center;
   gap: 20px;
   }

   .btn {
   display: inline-block;
   padding: 12px 30px;
   background-color: white;
   color: var(--primary);
   text-decoration: none;
   border-radius: 30px;
   font-weight: 600;
   transition: all 0.3s ease;
   border: 2px solid transparent;
   }

   .btn:hover {
   transform: translateY(-5px);
   box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
   }

   .btn-outlined {
   background-color: transparent;
   border: 2px solid white;
   color: white;
   }

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

   .floating-dbs {
   position: absolute;
   width: 100%;
   height: 100%;
   top: 0;
   left: 0;
   z-index: 1;
   }

   .db-icon {
   position: absolute;
   font-size: 2rem;
   opacity: 0.2;
   }

   #db1 {
   top: 20%;
   left: 15%;
   font-size: 3rem;
   }

   #db2 {
   top: 60%;
   left: 75%;
   font-size: 2.5rem;
   }

   #db3 {
   top: 30%;
   left: 85%;
   font-size: 4rem;
   }

   /* Features Section */
   .features {
   padding: 80px 0;
   background-color: white;
   }

   .section-header {
   text-align: center;
   margin-bottom: 60px;
   }

   .section-header h2 {
   font-size: 2.5rem;
   color: var(--dark);
   margin-bottom: 15px;
   }

   .section-header p {
   color: #64748b;
   max-width: 700px;
   margin: 0 auto;
   font-size: 1.1rem;
   }

   .features-grid {
   display: grid;
   grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
   gap: 30px;
   }

   .feature-card {
   background-color: white;
   border-radius: 10px;
   box-shadow: 0 5px 15px rgba(0, 0, 0, 0.05);
   padding: 30px;
   text-align: center;
   transition: transform 0.3s ease, box-shadow 0.3s ease;
   }

   .feature-card:hover {
   transform: translateY(-10px);
   box-shadow: 0 15px 30px rgba(0, 0, 0, 0.1);
   }

   .feature-icon {
   font-size: 2.5rem;
   color: var(--primary);
   margin-bottom: 20px;
   }

   .feature-card h3 {
   margin-bottom: 15px;
   color: var(--dark);
   }

   .feature-card p {
   color: #64748b;
   line-height: 1.6;
   }

   /* Learning Paths Section */
   .learning-paths {
   padding: 80px 0;
   background-color: #f8fafc;
   }

   .paths-container {
   display: grid;
   grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
   gap: 30px;
   }

   .path-card {
   background-color: white;
   border-radius: 10px;
   box-shadow: 0 5px 15px rgba(0, 0, 0, 0.05);
   overflow: hidden;
   transition: transform 0.3s ease, box-shadow 0.3s ease;
   opacity: 0;
   transform: translateY(30px);
   }

   .path-card.visible {
   opacity: 1;
   transform: translateY(0);
   }

   .path-card:hover {
   transform: translateY(-10px);
   box-shadow: 0 15px 30px rgba(0, 0, 0, 0.1);
   }

   .path-image {
   height: 120px;
   display: flex;
   align-items: center;
   justify-content: center;
   font-size: 3rem;
   color: white;
   }

   .path-content {
   padding: 20px;
   }

   .level-indicator {
   display: flex;
   gap: 5px;
   margin-bottom: 15px;
   }

   .level-dot {
   width: 12px;
   height: 12px;
   border-radius: 50%;
   background-color: #e2e8f0;
   }

   .level-dot.active {
   background-color: var(--success);
   }

   .path-content h3 {
   margin-bottom: 10px;
   color: var(--dark);
   }

   .path-content p {
   color: #64748b;
   margin-bottom: 20px;
   min-height: 70px;
   }

   /* About Section */
   .about {
   padding: 80px 0;
   background-color: white;
   }

   .about-content {
   display: flex;
   align-items: center;
   gap: 50px;
   }

   .about-image {
   flex: 1;
   text-align: center;
   opacity: 0;
   transform: translateX(-30px);
   }

   .about-image.visible {
   opacity: 1;
   transform: translateX(0);
   }

   .about-image img {
   max-width: 100%;
   border-radius: 10px;
   box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
   }

   .about-text {
   flex: 2;
   opacity: 0;
   transform: translateX(30px);
   }

   .about-text.visible {
   opacity: 1;
   transform: translateX(0);
   }

   .about-text h2 {
   font-size: 2.5rem;
   color: var(--dark);
   margin-bottom: 20px;
   }

   .about-text p {
   color: #64748b;
   margin-bottom: 15px;
   line-height: 1.7;
   }

   .social-links {
   display: flex;
   gap: 15px;
   margin-top: 30px;
   }

   .social-link {
   display: flex;
   align-items: center;
   justify-content: center;
   width: 40px;
   height: 40px;
   border-radius: 50%;
   background-color: var(--primary);
   color: white;
   text-decoration: none;
   transition: all 0.3s ease;
   }

   .social-link:hover {
   transform: translateY(-5px);
   background-color: var(--secondary);
   }

   /* Footer */
   footer {
   background-color: var(--primary);
   color: white;
   padding: 0px 0 18px;
   }



   .copyright {
   text-align: center;
   padding-top: 30px;
   border-top: 1px solid #334155;
   color: white;
   }

   /* Modal Styles */
   .modal {
   display: none;
   position: fixed;
   top: 0;
   left: 0;
   width: 100%;
   height: 100%;
   background-color: rgba(0, 0, 0, 0.7);
   z-index: 1000;
   overflow-y: auto;
   }

   .modal-content {
   background-color: white;
   max-width: 800px;
   margin: 50px auto;
   padding: 40px;
   border-radius: 10px;
   position: relative;
   box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
   }

   .close-modal {
   position: absolute;
   top: 20px;
   right: 20px;
   font-size: 1.5rem;
   cursor: pointer;
   color: #64748b;
   transition: color 0.3s ease;
   }

   .close-modal:hover {
   color: var(--danger);
   }

   .progress-bar {
   height: 8px;
   background-color: #e2e8f0;
   border-radius: 4px;
   margin: 20px 0 30px;
   overflow: hidden;
   }

   .progress {
   height: 100%;
   background-color: var(--primary);
   }

   .note-box {
   background-color: #e0f2fe;
   border-left: 4px solid var(--info);
   padding: 15px;
   margin: 20px 0;
   border-radius: 4px;
   }

   .example-box {
   background-color: #f8fafc;
   border: 1px solid #e2e8f0;
   padding: 20px;
   margin: 20px 0;
   border-radius: 4px;
   }

   .example-box h4 {
   margin-bottom: 10px;
   color: var(--primary);
   }

   .quiz-container {
   background-color: #f0f9ff;
   border: 1px solid #bae6fd;
   padding: 20px;
   margin: 30px 0;
   border-radius: 4px;
   }

   .quiz-container h3 {
   margin-bottom: 15px;
   }

   .quiz-options {
   list-style: none;
   margin-top: 15px;
   }

   .quiz-options li {
   margin-bottom: 10px;
   }

   .quiz-options label {
   display: flex;
   align-items: center;
   cursor: pointer;
   }

   .quiz-options input {
   margin-right: 10px;
   }

   .lessons-nav {
   display: flex;
   justify-content: space-between;
   margin-top: 40px;
   }

   .lesson-nav-btn {
   display: flex;
   align-items: center;
   gap: 10px;
   text-decoration: none;
   color: var(--primary);
   font-weight: 600;
   transition: all 0.3s ease;
   }

   .lesson-nav-btn:hover {
   color: var(--secondary);
   }

   .lesson-nav-btn.next {
   margin-left: auto;
   }

   /* Animation Classes */
   .fade-in {
   opacity: 0;
   transform: translateY(30px);
   transition: opacity 0.6s ease, transform 0.6s ease;
   }

   .fade-in.visible {
   opacity: 1;
   transform: translateY(0);
   }

   /* Responsive Styles */
   @media (max-width: 768px) {
   .hero h1 {
      font-size: 2.5rem;
   }

   .hero p {
      font-size: 1rem;
   }

   .cta-buttons {
      flex-direction: column;
      gap: 15px;
   }

   .menu-toggle {
      display: flex;
   }

   .nav-links {
      position: absolute;
      flex-direction: column;
      top: 70px;
      left: 0;
      right: 0;
      background-color: white;
      box-shadow: 0 10px 15px rgba(0, 0, 0, 0.1);
      padding: 20px;
      clip-path: polygon(0 0, 100% 0, 100% 0, 0 0);
      transition: all 0.3s ease;
   }

   .nav-links.active {
      clip-path: polygon(0 0, 100% 0, 100% 100%, 0 100%);
   }

   .nav-links li {
      margin: 15px 0;
      text-align: center;
   }

   .about-content {
      flex-direction: column;
   }

   .modal-content {
      margin: 20px;
      padding: 20px;
   }
   }



   /* ER Model Course Styles */


   /* Course Hero Section */
   .course-hero {
   background: var(--primary);
   color: white;
   padding: 4rem 0;
   text-align: center;
   }

   .course-hero h1 {
   font-size: 2.5rem;
   margin-bottom: 1rem;
   }

   .course-hero p {
   font-size: 1.2rem;
   max-width: 700px;
   margin: 0 auto 2rem;
   }

   .course-info {
   display: flex;
   justify-content: center;
   gap: 2rem;
   margin-top: 2rem;
   }

   .course-info-item {
   display: flex;
   align-items: center;
   gap: 0.5rem;
   }

   /* Course Navigation */
   .course-navigation {
   background-color: #fff;
   box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
   margin-bottom: 2rem;
   position: sticky;
   top: 73px;
   z-index: 900;
   }

   .course-nav-container {
   display: flex;
   overflow-x: auto;
   padding: 0.5rem 0;
   scrollbar-width: thin;
   }

   .course-nav-item {
   display: flex;
   align-items: center;
   padding: 0.75rem 1.5rem;
   border-radius: var(--border-radius);
   margin-right: 1rem;
   white-space: nowrap;
   transition: var(--transition);
   color: var(--dark);
   text-decoration: none;
   }

   .course-nav-item:hover {
   background-color: var(--light-gray);
   }


   .course-nav-item.active {
      background-color: var(--primary);
      color: white;
   }

   .course-nav-item .lesson-number {
      display: flex;
      align-items: center;
      justify-content: center;
      width: 30px;
      height: 30px;
      border-radius: 50%;
      background-color: var(--light-gray);
      color: var(--dark);
      font-weight: bold;
      margin-right: 1rem;
   }

   .course-nav-item.active .lesson-number {
      background-color: white;
      color: var(--primary);
   }

   .course-nav-item .lesson-info {
      display: flex;
      flex-direction: column;
   }

   .course-nav-item .lesson-info h3 {
      font-size: 1rem;
      margin-bottom: 0.25rem;
   }

   .course-nav-item .lesson-info p {
      font-size: 0.875rem;
      margin-bottom: 0;
      opacity: 0.8;
   }

   /* Course Content */
   .course-content {
      padding: 2rem 0 4rem;
   }

   .lesson {
      display: none;
      background-color: white;
      border-radius: var(--border-radius);
      box-shadow: var(--box-shadow);
      padding: 2rem;
      margin-bottom: 2rem;
   }

   .lesson.active {
      display: block;
      animation: fadeIn 0.5s ease;
   }

   .lesson-header {
      margin-bottom: 2rem;
      border-bottom: 1px solid var(--light-gray);
      padding-bottom: 1rem;
   }

   .progress-container {
      display: flex;
      align-items: center;
      gap: 1rem;
      margin-top: 1rem;
   }

   .progress-bar {
      flex: 1;
      height: 8px;
      background-color: var(--light-gray);
      border-radius: 4px;
      overflow: hidden;
   }

   .progress {
      height: 100%;
      background-color: var(--primary);
      border-radius: 4px;
   }

   .lesson-section {
      margin-bottom: 2.5rem;
   }

   .lesson-section h3 {
      color: var(--primary-dark);
      margin-bottom: 1rem;
   }

   /* Content Components */
   .note-box {
      background-color: #e7f5ff;
      border-left: 4px solid var(--info);
      padding: 1rem;
      border-radius: var(--border-radius);
      margin-bottom: 1.5rem;
   }

   .example-box {
      background-color: #f8f9fa;
      border: 1px solid #e9ecef;
      padding: 1.5rem;
      border-radius: var(--border-radius);
      margin-bottom: 1.5rem;
   }

   .example-box h4 {
      margin-bottom: 1rem;
      font-size: 1.25rem;
   }

   .image-container {
      margin-bottom: 1.5rem;
      text-align: center;
   }

   .image-container img {
      max-width: 100%;
      height: auto;
      border-radius: var(--border-radius);
      box-shadow: var(--box-shadow);
   }

   .image-caption {
      margin-top: 0.75rem;
      font-size: 0.875rem;
      color: var(--gray);
      font-style: italic;
   }

   /* Attribute Cards */
   .attributes-grid {
      display: grid;
      grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
      gap: 1.5rem;
      margin-bottom: 2rem;
   }

   .attribute-card {
      background-color: white;
      border-radius: var(--border-radius);
      padding: 1.5rem;
      box-shadow: var(--box-shadow);
      transition: var(--transition);
      border: 1px solid var(--light-gray);
   }

   .attribute-card:hover {
      transform: translateY(-5px);
      box-shadow: 0 6px 12px rgba(0, 0, 0, 0.15);
   }

   .attribute-icon {
      display: flex;
      align-items: center;
      justify-content: center;
      width: 50px;
      height: 50px;
      background-color: var(--light);
      border-radius: 50%;
      margin-bottom: 1rem;
   }

   .attribute-icon i {
      font-size: 1.5rem;
      color: var(--primary);
   }

   .attribute-card h4 {
      font-size: 1.25rem;
      margin-bottom: 0.5rem;
   }

   .attribute-card p {
      font-size: 0.875rem;
      color: var(--gray);
      margin-bottom: 0;
   }

   /* Relationship Cards */
   .relationship-types {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
      gap: 1.5rem;
      margin-bottom: 2rem;
   }

   .relationship-card {
      background-color: white;
      border-radius: var(--border-radius);
      padding: 1.5rem;
      box-shadow: var(--box-shadow);
      border: 1px solid var(--light-gray);
   }

   .relationship-diagram {
      display: flex;
      align-items: center;
      justify-content: space-between;
      margin: 1.5rem 0;
   }

   .relationship-line {
      flex: 1;
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding: 0 1rem;
   }

   .relationship-line hr {
      flex: 1;
      border: none;
      height: 2px;
      background-color: var(--primary);
   }

   .relationship-line span {
      font-weight: bold;
      color: var(--primary);
      padding: 0 0.5rem;
   }

   .entity {
      background-color: var(--light);
      padding: 0.75rem 1rem;
      border-radius: var(--border-radius);
      border: 1px solid var(--light-gray);
      font-weight: 500;
   }

   /* Concept Cards */
   .concept-types {
      display: grid;
      grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
      gap: 1.5rem;
      margin-bottom: 2rem;
   }

   .concept-card {
      background-color: white;
      border-radius: var(--border-radius);
      padding: 1.5rem;
      box-shadow: var(--box-shadow);
      border: 1px solid var(--light-gray);
   }

   .concept-card h4 {
      color: var(--primary-dark);
      font-size: 1.25rem;
      margin-bottom: 1rem;
   }

   .concept-card .image-container {
      margin: 1rem 0;
   }

   /* Mapping Rules */
   .mapping-rules {
      display: grid;
      grid-template-columns: 1fr;
      gap: 1.5rem;
      margin-bottom: 2rem;
   }

   .rule-card {
      background-color: white;
      border-radius: var(--border-radius);
      padding: 1.5rem;
      box-shadow: var(--box-shadow);
      border: 1px solid var(--light-gray);
   }

   .rule-card h4 {
      color: var(--primary-dark);
      font-size: 1.25rem;
      margin-bottom: 1rem;
      padding-bottom: 0.5rem;
      border-bottom: 1px solid var(--light-gray);
   }

   .example-snippet {
      background-color: #f8f9fa;
      padding: 1rem;
      border-radius: var(--border-radius);
      margin-top: 1rem;
   }

   .example-snippet code {
      font-family: 'Courier New', Courier, monospace;
      display: block;
      margin-bottom: 0.5rem;
   }

   /* Tabs */
   .tabs-container {
      background-color: white;
      border-radius: var(--border-radius);
      box-shadow: var(--box-shadow);
      overflow: hidden;
      margin-bottom: 2rem;
   }

   .tab-buttons {
      display: flex;
      border-bottom: 1px solid var(--light-gray);
   }

   .tab-btn {
      padding: 1rem 1.5rem;
      background: none;
      border: none;
      cursor: pointer;
      font-weight: 500;
      transition: var(--transition);
      flex: 1;
      text-align: center;
   }

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

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

   .tab-content {
      display: none;
      padding: 1.5rem;
   }

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

   .tab-content h5 {
      color: var(--primary-dark);
      margin-bottom: 1rem;
   }

   .code-block {
      background-color: #f8f9fa;
      padding: 1rem;
      border-radius: var(--border-radius);
      margin: 1rem 0;
   }

   .code-block code {
      font-family: 'Courier New', Courier, monospace;
      display: block;
      margin-bottom: 0.5rem;
   }

   /* Interactive Elements */
   .quiz-container, .interactive-exercise, .final-quiz {
      background-color: #f8f9fa;
      border-radius: var(--border-radius);
      padding: 1.5rem;
      margin-bottom: 2rem;
      border: 1px solid var(--light-gray);
   }

   .quiz-question {
      margin-bottom: 1.5rem;
   }

   .quiz-options {
      list-style: none;
      padding-left: 0;
   }

   .quiz-options li {
      margin-bottom: 0.75rem;
   }

   .quiz-options label {
      display: flex;
      align-items: center;
      cursor: pointer;
   }

   .quiz-options input[type="radio"] {
      margin-right: 0.75rem;
   }

   .quiz-feedback {
      margin-top: 1rem;
      padding: 0.75rem;
      border-radius: var(--border-radius);
      display: none;
   }

   .quiz-feedback.correct {
      display: block;
      background-color: #d4edda;
      color: #155724;
   }

   .quiz-feedback.incorrect {
      display: block;
      background-color: #f8d7da;
      color: #721c24;
   }

   .quiz-feedback.error {
      display: block;
      background-color: #fff3cd;
      color: #856404;
   }

   .exercise-item {
      margin-bottom: 1rem;
      padding-bottom: 1rem;
      border-bottom: 1px solid var(--light-gray);
   }

   .exercise-select {
      padding: 0.5rem;
      border-radius: var(--border-radius);
      border: 1px solid var(--light-gray);
      width: 100%;
      max-width: 300px;
      margin-top: 0.5rem;
   }

   .feedback {
      display: block;
      margin-top: 0.5rem;
      font-size: 0.875rem;
   }

   .feedback.correct {
      color: var(--success);
   }

   .feedback.incorrect {
      color: var(--danger);
   }

   .feedback.error {
      color: var(--warning);
   }

   /* Challenge Section */
   .challenge-section {
      background-color: #f8f9fa;
      border-radius: var(--border-radius);
      padding: 1.5rem;
      margin-bottom: 2rem;
      border: 1px solid var(--light-gray);
   }

   .challenge-description {
      background-color: white;
      padding: 1rem;
      border-radius: var(--border-radius);
      margin-bottom: 1.5rem;
      border: 1px solid var(--light-gray);
   }

   .solution-container {
      margin-top: 1.5rem;
      padding-top: 1.5rem;
      border-top: 1px solid var(--light-gray);
   }

   /* Case Study */
   .case-study {
      background-color: #f8f9fa;
      border-radius: var(--border-radius);
      padding: 1.5rem;
      margin-bottom: 2rem;
      border: 1px solid var(--light-gray);
   }

   .discussion-prompt {
      background-color: #e7f5ff;
      padding: 1rem;
      border-radius: var(--border-radius);
      margin-top: 1.5rem;
   }

   /* Course Completion */
   .course-completion {
      display: flex;
      flex-wrap: wrap;
      gap: 2rem;
      background-color: white;
      border-radius: var(--border-radius);
      padding: 2rem;
      box-shadow: var(--box-shadow);
      margin-bottom: 2rem;
   }

   .completion-badge {
      flex: 1;
      min-width: 250px;
      text-align: center;
      padding: 2rem;
      background-color: #f8f9fa;
      border-radius: var(--border-radius);
   }

   .completion-badge i {
      font-size: 4rem;
      color: var(--primary);
      margin-bottom: 1rem;
   }

   .next-steps {
      flex: 2;
      min-width: 300px;
   }

   .cta-buttons {
      display: flex;
      gap: 1rem;
      margin-top: 1.5rem;
   }

   /* Buttons */
   .btn {
      display: inline-block;
      padding: 0.75rem 1.5rem;
      background-color: var(--primary);
      color: white;
      border: none;
      border-radius: var(--border-radius);
      cursor: pointer;
      font-weight: 500;
      transition: var(--transition);
      text-align: center;
   }

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

   .btn-outline {
      background-color: transparent;
      border: 1px solid var(--primary);
      color: var(--primary);
   }

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

   .lesson-nav {
      display: flex;
      justify-content: space-between;
      margin-top: 3rem;
      padding-top: 1.5rem;
      border-top: 1px solid var(--light-gray);
   }

   .lesson-nav-btn {
      display: flex;
      align-items: center;
      gap: 0.5rem;
      padding: 0.75rem 1.5rem;
      background-color: var(--primary);
      color: white;
      border: none;
      border-radius: var(--border-radius);
      cursor: pointer;
      font-weight: 500;
      transition: var(--transition);
   }

   .lesson-nav-btn:hover {
      background-color: var(--primary-dark);
   }

   .lesson-nav-btn.next {
      background-color: var(--secondary);
   }

   .lesson-nav-btn.next:hover {
      background-color: #d06a18;
   }

   .lesson-nav-btn.disabled {
      background-color: var(--light-gray);
      color: var(--gray);
      cursor: not-allowed;
   }

   /* Animations */
   @keyframes fadeIn {
      from { opacity: 0; transform: translateY(20px); }
      to { opacity: 1; transform: translateY(0); }
   }

   .fade-in {
      opacity: 0;
      /* Initially invisible - GSAP will handle the animation */
   }

   /* Media Queries */
   @media (max-width: 768px) {
      .course-info {
         flex-direction: column;
         gap: 1rem;
         align-items: center;
      }
      
      .attributes-grid, .relationship-types, .concept-types {
         grid-template-columns: 1fr;
      }
      
      .menu-toggle {
         display: flex;
      }
      
      .nav-links {
         position: absolute;
         top: 100%;
         left: 0;
         width: 100%;
         flex-direction: column;
         background-color: white;
         padding: 1rem;
         box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
         transform: translateY(-10px);
         opacity: 0;
         pointer-events: none;
         transition: var(--transition);
      }
      
      .nav-links.active {
         transform: translateY(0);
         opacity: 1;
         pointer-events: all;
      }
      
      .menu-toggle.active span:nth-child(1) {
         transform: rotate(45deg) translate(5px, 5px);
      }
      
      .menu-toggle.active span:nth-child(2) {
         opacity: 0;
      }
      
      .menu-toggle.active span:nth-child(3) {
         transform: rotate(-45deg) translate(5px, -5px);
      }
      
      .course-hero h1 {
         font-size: 2rem;
      }
      
      .lesson {
         padding: 1.5rem;
      }
      
      .lesson-nav {
         flex-direction: column;
         gap: 1rem;
      }
      
      .lesson-nav-btn {
         width: 100%;
         justify-content: center;
      }
      
      .course-completion {
         flex-direction: column;
      }
   }

   @media (max-width: 576px) {
      .course-navigation{
         display: none;
      }
      .course-nav-container {
         flex-direction: column;
         gap: 0.5rem;
      }
      
      .course-nav-item {
         margin-right: 0;
      }
      
      .tab-buttons {
         flex-direction: column;
      }
      
      .tab-btn {
         border-bottom: 1px solid var(--light-gray);
      }
      
      .cta-buttons {
         flex-direction: column;
      }
   }

      .cta-buttons {
         display: flex;
         justify-content: center;
         gap: 20px;
      }
   
      .btn {
         display: inline-block;
         padding: 12px 30px;
         background-color: white;
         color: var(--primary);
         text-decoration: none;
         border-radius: 30px;
         font-weight: 600;
         transition: all 0.3s ease;
         border: 2px solid transparent;
      }