/* Missing Base Styles */

      /* CSS Variables - Add missing ones */

      /* Dark mode */
      [data-theme="dark"] {
        --bg-primary: var(--bg-primary-dark);
        --bg-secondary: var(--bg-secondary-dark);
        --text-primary: var(--text-primary-dark);
        --text-secondary: var(--text-secondary-dark);
        --border-color: var(--border-color-dark);
      }

      /* Base Typography */

      /* Container */
      .container {
        max-width: 1200px;
        margin: 0 auto;
        padding: 0 var(--space-6);
      }

      /* Grid System */
      .grid {
        display: grid;
        gap: var(--space-8);
      }

      .grid-responsive {
        grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
      }

      @media (max-width: 768px) {
        .grid-responsive {
          grid-template-columns: 1fr;
        }
      }

      /* Section Styling */
      .section {
        padding: var(--space-16) 0;
      }

      .section-title {
        font-family: var(--font-family-brand);
        font-size: 2.5rem;
        font-weight: var(--font-weight-bold);
        text-align: center;
        margin-bottom: var(--space-6);
        color: var(--text-primary);
      }

      .section-subtitle {
        text-align: center;
        font-size: 1.125rem;
        color: var(--text-secondary);
        margin-bottom: var(--space-12);
        max-width: 600px;
        margin-left: auto;
        margin-right: auto;
      }

      /* Button Styles */
      .btn {
        display: inline-flex;
        align-items: center;
        gap: var(--space-2);
        padding: var(--space-3) var(--space-6);
        border-radius: var(--radius-lg);
        font-weight: var(--font-weight-medium);
        text-decoration: none;
        transition: all var(--transition-normal);
        cursor: pointer;
        border: none;
        font-size: 1rem;
      }

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

      .btn-primary:hover {
        background: #4f46e5;
        transform: translateY(-2px);
        box-shadow: var(--shadow-lg);
      }

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

      .btn-secondary:hover {
        background: var(--ai-primary);
        color: white;
        transform: translateY(-2px);
      }

      /* Text Utilities */
      .text-lg {
        font-size: 1.125rem;
      }

      .text-secondary {
        color: var(--text-secondary);
      }

      /* Skip Link */
      .skip-link {
        position: absolute;
        top: -40px;
        left: 6px;
        background: var(--ai-primary);
        color: white;
        padding: 8px;
        text-decoration: none;
        border-radius: var(--radius-md);
        z-index: 1000;
      }

      .skip-link:focus {
        top: 6px;
      }

      /* Main Content */
      .main-content {
        min-height: 60vh;
        padding-top: var(--space-8);
      }

      /* Mobile responsive improvements */
      @media (max-width: 768px) {
        .container {
          padding: 0 var(--space-4);
        }

        .section {
          padding: var(--space-12) 0;
        }

        .section-title {
          font-size: 2rem;
        }

        .cta-buttons {
          flex-direction: column;
          align-items: center;
        }

        .btn {
          width: 100%;
          justify-content: center;
          max-width: 280px;
        }
      }

      /* AI-themed cards */
      .ai-card {
        background: var(--bg-primary);
        border: 1px solid var(--border-color);
        border-radius: var(--radius-lg);
        padding: var(--space-8);
        text-decoration: none;
        color: inherit;
        transition: all var(--transition-normal);
        box-shadow: var(--shadow-sm);
        position: relative;
        overflow: hidden;
        display: flex;
        flex-direction: column;
        height: 100%;
      }

      .ai-card::before {
        content: "";
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 4px;
        background: var(--ai-gradient);
        transform: scaleX(0);
        transform-origin: left;
        transition: transform var(--transition-normal);
      }

      .ai-card:hover,
      .ai-card:focus {
        transform: translateY(-8px);
        box-shadow: var(--shadow-xl);
        border-color: var(--ai-primary);
        outline: none;
      }

      .ai-card:hover::before,
      .ai-card:focus::before {
        transform: scaleX(1);
      }

      .ai-card-header {
        display: flex;
        align-items: center;
        gap: var(--space-6);
        margin-bottom: var(--space-6);
      }

      .ai-icon {
        width: 70px;
        height: 70px;
        border-radius: var(--radius-lg);
        display: flex;
        align-items: center;
        justify-content: center;
        font-size: 1.75rem;
        color: white;
        flex-shrink: 0;
        position: relative;
        overflow: hidden;
      }

      .ai-icon.brain {
        background: var(--brain-gradient);
      }
      .ai-icon.neural {
        background: var(--neural-gradient);
      }
      .ai-icon.future {
        background: var(--future-gradient);
      }
      .ai-icon.learning {
        background: linear-gradient(
          135deg,
          var(--success-color) 0%,
          #059669 100%
        );
      }
      .ai-icon.ethics {
        background: linear-gradient(
          135deg,
          var(--warning-color) 0%,
          #d97706 100%
        );
      }
      .ai-icon.tools {
        background: linear-gradient(135deg, var(--info-color) 0%, #1e40af 100%);
      }

      .ai-card-info h3 {
        font-size: 1.5rem;
        font-weight: var(--font-weight-semibold);
        margin-bottom: var(--space-2);
        color: var(--text-primary);
      }

      .ai-card-level {
        display: inline-block;
        padding: var(--space-1) var(--space-3);
        background: var(--ai-secondary);
        color: white;
        font-size: 0.75rem;
        font-weight: var(--font-weight-semibold);
        border-radius: var(--radius-full);
        text-transform: uppercase;
        letter-spacing: 0.5px;
      }

      .ai-card-description {
        color: var(--text-secondary);
        margin-bottom: var(--space-6);
        line-height: 1.7;
        flex-grow: 1;
      }

      .ai-card-features {
        list-style: none;
        margin-bottom: var(--space-6);
      }

      .ai-card-features li {
        display: flex;
        align-items: flex-start;
        gap: var(--space-3);
        margin-bottom: var(--space-3);
        font-size: 0.95rem;
        color: var(--text-secondary);
        line-height: 1.5;
      }

      .ai-card-features li i {
        color: var(--ai-accent);
        width: 18px;
        flex-shrink: 0;
        margin-top: 2px;
      }

      .ai-card-cta {
        display: flex;
        align-items: center;
        justify-content: space-between;
        padding-top: var(--space-6);
        border-top: 1px solid var(--border-light);
        margin-top: auto;
      }

      .cta-text {
        color: var(--ai-primary);
        font-weight: var(--font-weight-semibold);
        font-size: 0.95rem;
      }

      .cta-arrow {
        color: var(--ai-primary);
        transition: transform var(--transition-normal);
      }

      .ai-card:hover .cta-arrow {
        transform: translateX(5px);
      }

      /* Intro section */
      .intro-section {
        background: var(--bg-secondary);
        border-radius: var(--radius-xl);
        padding: var(--space-16) var(--space-8);
        text-align: center;
        margin-bottom: var(--space-20);
        position: relative;
        overflow: hidden;
      }

      .intro-section::before {
        content: "🤖";
        position: absolute;
        top: var(--space-8);
        right: var(--space-8);
        font-size: 3rem;
        opacity: 0.1;
        animation: bounce 2s ease-in-out infinite;
      }

      @keyframes bounce {
        0%,
        100% {
          transform: translateY(0px);
        }
        50% {
          transform: translateY(-10px);
        }
      }

      /* FAQ Section */
      .faq-item {
        background: var(--bg-primary);
        border: 1px solid var(--border-color);
        border-radius: var(--radius-lg);
        margin-bottom: var(--space-4);
        overflow: hidden;
      }

      .faq-question {
        width: 100%;
        background: none;
        border: none;
        padding: var(--space-6);
        text-align: left;
        font-size: 1.1rem;
        font-weight: var(--font-weight-medium);
        color: var(--text-primary);
        cursor: pointer;
        display: flex;
        align-items: center;
        justify-content: space-between;
        transition: all var(--transition-normal);
      }

      .faq-question:hover {
        background: var(--bg-secondary);
      }

      .faq-question i {
        color: var(--ai-primary);
        transition: transform var(--transition-normal);
      }

      .faq-item.active .faq-question i {
        transform: rotate(180deg);
      }

      .faq-answer {
        padding: 0 var(--space-6);
        max-height: 0;
        overflow: hidden;
        transition: all var(--transition-normal);
      }

      .faq-item.active .faq-answer {
        max-height: 300px;
        padding: 0 var(--space-6) var(--space-6);
      }

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

      /* CTA Section */
      .cta-section {
        background: var(--ai-gradient);
        color: white;
        text-align: center;
        padding: var(--space-16) var(--space-8);
        border-radius: var(--radius-xl);
        margin: var(--space-16) 0;
        position: relative;
        overflow: hidden;
      }

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

      .cta-title {
        font-size: 2.5rem;
        font-weight: var(--font-weight-bold);
        margin-bottom: var(--space-4);
        line-height: 1.2;
      }

      .cta-subtitle {
        font-size: 1.125rem;
        margin-bottom: var(--space-8);
        opacity: 0.9;
        max-width: 600px;
        margin-left: auto;
        margin-right: auto;
      }

      .cta-buttons {
        display: flex;
        gap: var(--space-4);
        justify-content: center;
        flex-wrap: wrap;
      }

      /* Mobile responsive */
      @media (max-width: 768px) {
        .hero {
          padding: calc(var(--header-height-mobile) + var(--space-8)) 0
            var(--space-12);
        }

        .hero-title {
          font-size: 2.5rem;
        }

        .cta-title {
          font-size: 2rem;
        }

        .ai-card-header {
          flex-direction: column;
          text-align: center;
          gap: var(--space-4);
        }

        .faq-question {
          font-size: 1rem;
        }

        .intro-section::before {
          font-size: 2rem;
          top: var(--space-4);
          right: var(--space-4);
        }
      }

/* AI-specific styling that extends the main design system */


      .hero::before {
        content: "";
        position: absolute;
        top: 0;
        left: 0;
        right: 0;
        bottom: 0;
        background: url("../images/hero.webp") rgba(255, 255, 255, 0.1);
        background-blend-mode: overlay;
        background-size: 1200px 800px;
        background-position: center;
        opacity: 0.9;
        animation: float 20s ease-in-out infinite;
      }

      @keyframes float {
        0%,
        100% {
          transform: translateY(0px);
        }
        50% {
          transform: translateY(-10px);
        }
      }




      /* AI-themed cards */
      .ai-card {
        background: var(--bg-primary);
        border: 1px solid var(--border-color);
        border-radius: var(--radius-lg);
        padding: var(--space-8);
        text-decoration: none;
        color: inherit;
        transition: all var(--transition-normal);
        box-shadow: var(--shadow-sm);
        position: relative;
        overflow: hidden;
        display: flex;
        flex-direction: column;
        height: 100%;
      }

      .ai-card::before {
        content: "";
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 4px;
        background: var(--ai-gradient);
        transform: scaleX(0);
        transform-origin: left;
        transition: transform var(--transition-normal);
      }

      .ai-card:hover,
      .ai-card:focus {
        transform: translateY(-8px);
        box-shadow: var(--shadow-xl);
        border-color: var(--ai-primary);
        outline: none;
      }

      .ai-card:hover::before,
      .ai-card:focus::before {
        transform: scaleX(1);
      }

      .ai-card-header {
        display: flex;
        align-items: center;
        gap: var(--space-6);
        margin-bottom: var(--space-6);
      }

      .ai-icon {
        width: 70px;
        height: 70px;
        border-radius: var(--radius-lg);
        display: flex;
        align-items: center;
        justify-content: center;
        font-size: 1.75rem;
        color: white;
        flex-shrink: 0;
        position: relative;
        overflow: hidden;
      }

      .ai-icon.brain {
        background: var(--brain-gradient);
      }
      .ai-icon.neural {
        background: var(--neural-gradient);
      }
      .ai-icon.future {
        background: var(--future-gradient);
      }
      .ai-icon.learning {
        background: linear-gradient(
          135deg,
          var(--success-color) 0%,
          #059669 100%
        );
      }
      .ai-icon.ethics {
        background: linear-gradient(
          135deg,
          var(--warning-color) 0%,
          #d97706 100%
        );
      }
      .ai-icon.tools {
        background: linear-gradient(135deg, var(--info-color) 0%, #1e40af 100%);
      }

      .ai-card-info h3 {
        font-size: 1.5rem;
        font-weight: var(--font-weight-semibold);
        margin-bottom: var(--space-2);
        color: var(--text-primary);
      }

      .ai-card-level {
        display: inline-block;
        padding: var(--space-1) var(--space-3);
        background: var(--ai-secondary);
        color: white;
        font-size: 0.75rem;
        font-weight: var(--font-weight-semibold);
        border-radius: var(--radius-full);
        text-transform: uppercase;
        letter-spacing: 0.5px;
      }

      .ai-card-description {
        color: var(--text-secondary);
        margin-bottom: var(--space-6);
        line-height: 1.7;
        flex-grow: 1;
      }

      .ai-card-features {
        list-style: none;
        margin-bottom: var(--space-6);
      }

      .ai-card-features li {
        display: flex;
        align-items: flex-start;
        gap: var(--space-3);
        margin-bottom: var(--space-3);
        font-size: 0.95rem;
        color: var(--text-secondary);
        line-height: 1.5;
      }

      .ai-card-features li i {
        color: var(--ai-accent);
        width: 18px;
        flex-shrink: 0;
        margin-top: 2px;
      }

      .ai-card-cta {
        display: flex;
        align-items: center;
        justify-content: space-between;
        padding-top: var(--space-6);
        border-top: 1px solid var(--border-light);
        margin-top: auto;
      }

      .cta-text {
        color: var(--ai-primary);
        font-weight: var(--font-weight-semibold);
        font-size: 0.95rem;
      }

      .cta-arrow {
        color: var(--ai-primary);
        transition: transform var(--transition-normal);
      }

      .ai-card:hover .cta-arrow {
        transform: translateX(5px);
      }

      /* Intro section */
      .intro-section {
        background: var(--bg-secondary);
        border-radius: var(--radius-xl);
        padding: var(--space-16) var(--space-8);
        text-align: center;
        margin-bottom: var(--space-20);
        position: relative;
        overflow: hidden;
      }

      .intro-section::before {
        content: "🤖";
        position: absolute;
        top: var(--space-8);
        right: var(--space-8);
        font-size: 3rem;
        opacity: 0.1;
        animation: bounce 2s ease-in-out infinite;
      }

      @keyframes bounce {
        0%,
        100% {
          transform: translateY(0px);
        }
        50% {
          transform: translateY(-10px);
        }
      }

      /* FAQ Section */
      .faq-item {
        background: var(--bg-primary);
        border: 1px solid var(--border-color);
        border-radius: var(--radius-lg);
        margin-bottom: var(--space-4);
        overflow: hidden;
      }

      .faq-question {
        width: 100%;
        background: none;
        border: none;
        padding: var(--space-6);
        text-align: left;
        font-size: 1.1rem;
        font-weight: var(--font-weight-medium);
        color: var(--text-primary);
        cursor: pointer;
        display: flex;
        align-items: center;
        justify-content: space-between;
        transition: all var(--transition-normal);
      }

      .faq-question:hover {
        background: var(--bg-secondary);
      }

      .faq-question i {
        color: var(--ai-primary);
        transition: transform var(--transition-normal);
      }

      .faq-item.active .faq-question i {
        transform: rotate(180deg);
      }

      .faq-answer {
        padding: 0 var(--space-6);
        max-height: 0;
        overflow: hidden;
        transition: all var(--transition-normal);
      }

      .faq-item.active .faq-answer {
        max-height: 300px;
        padding: 0 var(--space-6) var(--space-6);
      }

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

      /* CTA Section */
      .cta-section {
        background: var(--ai-gradient);
        color: white;
        text-align: center;
        padding: var(--space-16) var(--space-8);
        border-radius: var(--radius-xl);
        margin: var(--space-16) 0;
        position: relative;
        overflow: hidden;
      }

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

      .cta-title {
        font-size: 2.5rem;
        font-weight: var(--font-weight-bold);
        margin-bottom: var(--space-4);
        line-height: 1.2;
      }

      .cta-subtitle {
        font-size: 1.125rem;
        margin-bottom: var(--space-8);
        opacity: 0.9;
        max-width: 600px;
        margin-left: auto;
        margin-right: auto;
      }

      .cta-buttons {
        display: flex;
        gap: var(--space-4);
        justify-content: center;
        flex-wrap: wrap;
      }

      /* Mobile responsive */
      @media (max-width: 768px) {
        .hero {
          padding: calc(var(--header-height-mobile) + var(--space-8)) 0
            var(--space-12);
        }

        .hero-title {
          font-size: 2.5rem;
        }

        .cta-title {
          font-size: 2rem;
        }

        .ai-card-header {
          flex-direction: column;
          text-align: center;
          gap: var(--space-4);
        }

        .faq-question {
          font-size: 1rem;
        }

        .intro-section::before {
          font-size: 2rem;
          top: var(--space-4);
          right: var(--space-4);
        }
      }

/* AI Playground Styles */
      .ai-playground {
        background: var(--bg-primary);
        border: 1px solid var(--border-color);
        border-radius: var(--radius-xl);
        overflow: hidden;
        box-shadow: var(--shadow-lg);
      }

      .playground-tabs {
        display: flex;
        background: var(--bg-secondary);
        border-bottom: 1px solid var(--border-color);
        overflow-x: auto;
      }

      .playground-tab {
        flex: 1;
        padding: var(--space-4) var(--space-6);
        background: none;
        border: none;
        color: var(--text-secondary);
        font-weight: var(--font-weight-medium);
        cursor: pointer;
        transition: all var(--transition-normal);
        display: flex;
        align-items: center;
        justify-content: center;
        gap: var(--space-2);
        border-bottom: 3px solid transparent;
      }

      .playground-tab:hover {
        background: rgba(99, 102, 241, 0.1);
        color: var(--ai-primary);
      }

      .playground-tab.active {
        background: white;
        color: var(--ai-primary);
        border-bottom-color: var(--ai-primary);
      }

      .playground-content {
        padding: var(--space-8);
      }

      .demo-panel {
        display: none;
      }

      .demo-panel.active {
        display: block;
        animation: fadeIn 0.3s ease;
      }

      .demo-panel h3 {
        font-size: 1.5rem;
        margin-bottom: var(--space-4);
        color: var(--text-primary);
      }

      .demo-panel p {
        color: var(--text-secondary);
        margin-bottom: var(--space-6);
      }

      .pattern-grid {
        display: grid;
        grid-template-columns: repeat(5, 1fr);
        gap: var(--space-2);
        margin-bottom: var(--space-6);
        max-width: 400px;
      }

      .pattern-cell {
        aspect-ratio: 1;
        border-radius: var(--radius-md);
        cursor: pointer;
        transition: all var(--transition-fast);
        border: 2px solid var(--border-color);
        background: white;
      }

      .pattern-cell:hover {
        transform: scale(1.1);
        box-shadow: var(--shadow-md);
      }

      .pattern-cell.red {
        background: #ef4444;
        border-color: #dc2626;
      }
      .pattern-cell.blue {
        background: #3b82f6;
        border-color: #2563eb;
      }
      .pattern-cell.green {
        background: #10b981;
        border-color: #059669;
      }
      .pattern-cell.yellow {
        background: #f59e0b;
        border-color: #d97706;
      }
      .pattern-cell.purple {
        background: #8b5cf6;
        border-color: #7c3aed;
      }

      #sentimentText,
      #predictionText {
        width: 100%;
        padding: var(--space-4);
        border: 2px solid var(--border-color);
        border-radius: var(--radius-lg);
        font-family: var(--font-family-base);
        font-size: 1rem;
        margin-bottom: var(--space-6);
        resize: vertical;
        transition: border-color var(--transition-normal);
      }

      #sentimentText:focus,
      #predictionText:focus {
        outline: none;
        border-color: var(--ai-primary);
        box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
      }

      .demo-controls {
        display: flex;
        gap: var(--space-4);
        margin-bottom: var(--space-6);
        flex-wrap: wrap;
      }

      .demo-result {
        padding: var(--space-6);
        background: var(--bg-secondary);
        border-radius: var(--radius-lg);
        min-height: 80px;
        display: none;
        animation: slideDown 0.3s ease;
      }

      .demo-result.show {
        display: block;
      }

      .result-emoji {
        font-size: 2rem;
        margin-bottom: var(--space-2);
      }

      /* AI Timeline Styles */
      .ai-timeline {
        position: relative;
        max-width: 900px;
        margin: 0 auto;
        padding: var(--space-4) 0;
      }

      .ai-timeline::before {
        content: "";
        position: absolute;
        left: 50%;
        transform: translateX(-50%);
        width: 3px;
        height: 100%;
        background: linear-gradient(
          to bottom,
          var(--ai-primary),
          var(--ai-accent)
        );
      }

      .timeline-item {
        display: flex;
        margin-bottom: var(--space-12);
        position: relative;
      }

      .timeline-item:nth-child(odd) {
        flex-direction: row;
      }

      .timeline-item:nth-child(even) {
        flex-direction: row-reverse;
      }

      .timeline-marker {
        width: 60px;
        height: 60px;
        background: var(--ai-gradient);
        border-radius: 50%;
        display: flex;
        align-items: center;
        justify-content: center;
        color: white;
        font-size: 1.5rem;
        flex-shrink: 0;
        position: absolute;
        left: 50%;
        transform: translateX(-50%);
        z-index: 2;
        box-shadow: 0 0 0 8px var(--bg-primary);
      }

      .timeline-content {
        width: calc(50% - 50px);
        background: var(--bg-primary);
        border: 1px solid var(--border-color);
        border-radius: var(--radius-lg);
        padding: var(--space-6);
        box-shadow: var(--shadow-md);
        transition: all var(--transition-normal);
      }

      .timeline-item:nth-child(odd) .timeline-content {
        margin-right: auto;
        margin-left: var(--space-4);
      }

      .timeline-item:nth-child(even) .timeline-content {
        margin-left: auto;
        margin-right: var(--space-4);
      }

      .timeline-content:hover {
        transform: translateY(-5px);
        box-shadow: var(--shadow-xl);
        border-color: var(--ai-primary);
      }

      .timeline-content h3 {
        color: var(--ai-primary);
        font-size: 1.25rem;
        margin-bottom: var(--space-3);
      }

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

      /* Quiz Styles */
      .ai-quiz {
        max-width: 700px;
        margin: 0 auto;
        background: var(--bg-primary);
        border: 1px solid var(--border-color);
        border-radius: var(--radius-xl);
        padding: var(--space-8);
        box-shadow: var(--shadow-lg);
      }

      .quiz-question {
        display: none;
      }

      .quiz-question.active {
        display: block;
        animation: fadeIn 0.3s ease;
      }

      .quiz-question h3 {
        color: var(--ai-primary);
        font-size: 0.9rem;
        text-transform: uppercase;
        letter-spacing: 1px;
        margin-bottom: var(--space-4);
      }

      .question-text {
        font-size: 1.5rem;
        font-weight: var(--font-weight-semibold);
        color: var(--text-primary);
        margin-bottom: var(--space-8);
        line-height: 1.4;
      }

      .quiz-options {
        display: flex;
        flex-direction: column;
        gap: var(--space-4);
      }

      .quiz-option {
        display: flex;
        align-items: center;
        gap: var(--space-4);
        padding: var(--space-4) var(--space-6);
        background: var(--bg-secondary);
        border: 2px solid var(--border-color);
        border-radius: var(--radius-lg);
        cursor: pointer;
        transition: all var(--transition-normal);
        text-align: left;
        width: 100%;
      }

      .quiz-option:hover {
        background: rgba(99, 102, 241, 0.05);
        border-color: var(--ai-primary);
        transform: translateX(5px);
      }

      .quiz-option.selected {
        background: var(--ai-primary);
        border-color: var(--ai-primary);
        color: white;
      }

      .quiz-option.correct {
        background: var(--success-color);
        border-color: var(--success-color);
        color: white;
      }

      .quiz-option.incorrect {
        background: var(--error-color);
        border-color: var(--error-color);
        color: white;
      }

      .quiz-option.disabled {
        pointer-events: none;
        opacity: 0.6;
      }

      .option-letter {
        width: 36px;
        height: 36px;
        background: white;
        color: var(--ai-primary);
        border-radius: 50%;
        display: flex;
        align-items: center;
        justify-content: center;
        font-weight: var(--font-weight-bold);
        flex-shrink: 0;
      }

      .quiz-option.selected .option-letter,
      .quiz-option.correct .option-letter,
      .quiz-option.incorrect .option-letter {
        background: rgba(255, 255, 255, 0.3);
        color: white;
      }

      .option-text {
        font-size: 1.05rem;
        font-weight: var(--font-weight-medium);
      }

      .quiz-feedback {
        margin-top: var(--space-6);
        padding: var(--space-6);
        border-radius: var(--radius-lg);
        display: none;
        animation: slideDown 0.3s ease;
      }

      .quiz-feedback.show {
        display: block;
      }

      .quiz-feedback.correct {
        background: rgba(16, 185, 129, 0.1);
        border: 2px solid var(--success-color);
        color: var(--success-color);
      }

      .quiz-feedback.incorrect {
        background: rgba(239, 68, 68, 0.1);
        border: 2px solid var(--error-color);
        color: var(--error-color);
      }

      .quiz-feedback strong {
        display: block;
        font-size: 1.1rem;
        margin-bottom: var(--space-2);
      }

      .quiz-results {
        display: none;
        text-align: center;
      }

      .quiz-results.show {
        display: block;
        animation: fadeIn 0.5s ease;
      }

      .quiz-results h3 {
        font-size: 2rem;
        color: var(--text-primary);
        margin-bottom: var(--space-4);
      }

      .results-score {
        font-size: 3rem;
        font-weight: var(--font-weight-bold);
        color: var(--ai-primary);
        margin: var(--space-6) 0;
      }

      .results-message {
        font-size: 1.2rem;
        color: var(--text-secondary);
        margin-bottom: var(--space-8);
      }

      /* Resources Grid */
      .resources-grid {
        display: grid;
        grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
        gap: var(--space-6);
      }

      .resource-card {
        background: var(--bg-primary);
        border: 1px solid var(--border-color);
        border-radius: var(--radius-lg);
        padding: var(--space-8);
        text-decoration: none;
        color: inherit;
        transition: all var(--transition-normal);
        display: flex;
        flex-direction: column;
        align-items: center;
        text-align: center;
        position: relative;
      }

      .resource-card:hover {
        transform: translateY(-5px);
        box-shadow: var(--shadow-xl);
        border-color: var(--ai-primary);
      }

      .resource-icon {
        width: 80px;
        height: 80px;
        background: var(--ai-gradient);
        border-radius: 50%;
        display: flex;
        align-items: center;
        justify-content: center;
        color: white;
        font-size: 2rem;
        margin-bottom: var(--space-6);
      }

      .resource-card h3 {
        font-size: 1.25rem;
        color: var(--text-primary);
        margin-bottom: var(--space-3);
      }

      .resource-card p {
        color: var(--text-secondary);
        margin-bottom: var(--space-4);
        line-height: 1.6;
      }

      .resource-tag {
        display: inline-block;
        padding: var(--space-1) var(--space-3);
        background: var(--ai-primary);
        color: white;
        font-size: 0.75rem;
        font-weight: var(--font-weight-semibold);
        border-radius: var(--radius-full);
        text-transform: uppercase;
      }

      /* Video Grid */
      .video-grid {
        display: grid;
        grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
        gap: var(--space-8);
      }

      .video-card {
        background: var(--bg-primary);
        border: 1px solid var(--border-color);
        border-radius: var(--radius-lg);
        overflow: hidden;
        transition: all var(--transition-normal);
        cursor: pointer;
      }

      .video-card:hover {
        transform: translateY(-5px);
        box-shadow: var(--shadow-xl);
      }

      .video-thumbnail {
        position: relative;
        background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
        height: 180px;
        display: flex;
        align-items: center;
        justify-content: center;
        color: white;
        font-size: 4rem;
        transition: all var(--transition-normal);
      }

      .video-card:hover .video-thumbnail {
        background: linear-gradient(135deg, #764ba2 0%, #667eea 100%);
      }

      .video-thumbnail i {
        opacity: 0.9;
      }

      .video-duration {
        position: absolute;
        bottom: var(--space-3);
        right: var(--space-3);
        background: rgba(0, 0, 0, 0.8);
        color: white;
        padding: var(--space-1) var(--space-3);
        border-radius: var(--radius-md);
        font-size: 0.85rem;
        font-weight: var(--font-weight-semibold);
      }

      .video-info {
        padding: var(--space-6);
      }

      .video-info h3 {
        font-size: 1.125rem;
        color: var(--text-primary);
        margin-bottom: var(--space-3);
        line-height: 1.4;
      }

      .video-info p {
        color: var(--text-secondary);
        margin-bottom: var(--space-4);
        line-height: 1.5;
      }

      .video-tag {
        display: inline-block;
        padding: var(--space-1) var(--space-3);
        background: rgba(99, 102, 241, 0.1);
        color: var(--ai-primary);
        font-size: 0.75rem;
        font-weight: var(--font-weight-semibold);
        border-radius: var(--radius-full);
      }

      /* Mobile responsive - extended */
      @media (max-width: 768px) {
        .playground-tabs {
          flex-direction: column;
        }

        .playground-tab {
          border-bottom: 1px solid var(--border-color);
          border-left: 3px solid transparent;
        }

        .playground-tab.active {
          border-left-color: var(--ai-primary);
          border-bottom-color: var(--border-color);
        }

        .pattern-grid {
          grid-template-columns: repeat(5, 1fr);
          max-width: 100%;
        }

        .ai-timeline::before {
          left: 30px;
        }

        .timeline-marker {
          left: 30px;
          width: 50px;
          height: 50px;
          font-size: 1.25rem;
        }

        .timeline-item {
          flex-direction: row !important;
        }

        .timeline-content {
          width: calc(100% - 80px);
          margin-left: 80px !important;
          margin-right: 0 !important;
        }

        .resources-grid {
          grid-template-columns: 1fr;
        }

        .video-grid {
          grid-template-columns: 1fr;
        }
      }

/* Ensure mobile dropdowns work properly */
      @media (max-width: 768px) {
        /* FORCE mobile menu to display full width */
        .nav-links,
        #navLinks,
        ul.nav-links {
          display: flex !important;
          position: fixed !important;
          top: 70px !important;
          left: 0 !important;
          right: 0 !important;
          bottom: 0 !important;
          width: 100vw !important;
          height: auto !important;
          min-height: calc(100vh - 70px) !important;
        }

        .nav-links.active,
        #navLinks.active,
        ul.nav-links.active {
          display: flex !important;
          max-height: calc(100vh - 70px) !important;
          height: auto !important;
        }

        /* Make sure nav links with dropdowns are clearly tappable */
        .nav-item .nav-link {
          position: relative;
          user-select: none;
          -webkit-user-select: none;
          -webkit-tap-highlight-color: rgba(70, 187, 229, 0.2);
          cursor: pointer;
        }

        /* Ensure chevron is visible and clickable */
        .nav-link .fa-chevron-down {
          transition: transform 0.3s ease !important;
          opacity: 1 !important;
          pointer-events: none; /* Let clicks go through to parent link */
        }

        /* Visual feedback when dropdown is open */
        .nav-item.mobile-open > .nav-link,
        .nav-item.mobile-dropdown-open > .nav-link {
          background: rgba(70, 187, 229, 0.15) !important;
          border-color: var(--primary-color, #46bbe5) !important;
        }

        /* Make dropdowns smoother */
        .dropdown {
          transition: max-height 0.4s cubic-bezier(0.4, 0, 0.2, 1),
            padding 0.4s cubic-bezier(0.4, 0, 0.2, 1) !important;
        }

        /* Ensure dropdown items are visible when parent is open */
        .nav-item.mobile-open .dropdown,
        .nav-item.mobile-dropdown-open .dropdown {
          display: block !important;
          visibility: visible !important;
          opacity: 1 !important;
          pointer-events: auto !important;
        }

        /* Ensure dropdown items are clickable */
        .dropdown-item,
        .dropdown > a {
          pointer-events: auto !important;
          touch-action: manipulation !important;
          user-select: none;
          -webkit-user-select: none;
        }
      }