* {
        margin: 0;
        padding: 0;
        box-sizing: border-box;
      }

      :root {
        --primary: #3ddc84;
        --primary-dark: #2db56f;
        --secondary: #4285f4;
        --background: #0f0f0f;
        --surface: #1a1a1a;
        --surface-hover: #252525;
        --text-primary: #ffffff;
        --text-secondary: #b3b3b3;
        --shadow: rgba(61, 220, 132, 0.1);
        --shadow-hover: rgba(61, 220, 132, 0.2);
      }

      body {
        font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
        background: var(--background);
        color: var(--text-primary);
        line-height: 1.6;
        overflow-x: hidden;
      }

      /* Background Animation */
      body::before {
        content: '';
        position: fixed;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background: 
          radial-gradient(circle at 20% 30%, rgba(61, 220, 132, 0.05) 0%, transparent 50%),
          radial-gradient(circle at 80% 70%, rgba(66, 133, 244, 0.05) 0%, transparent 50%);
        pointer-events: none;
        z-index: 0;
      }

      .container {
        max-width: 1200px;
        margin: 0 auto;
        padding: 60px 24px;
        position: relative;
        z-index: 1;
      }

      /* Header Section */
      .header-section {
        text-align: center;
        margin-bottom: 60px;
        animation: fadeInUp 0.8s ease-out;
      }

      .logo-container {
        display: inline-flex;
        align-items: center;
        justify-content: center;
        width: 80px;
        height: 80px;
        background: linear-gradient(135deg, var(--primary), var(--secondary));
        border-radius: 20px;
        margin-bottom: 24px;
        font-size: 40px;
        box-shadow: 0 10px 30px var(--shadow);
        animation: float 3s ease-in-out infinite;
      }

      h1 {
        font-size: clamp(2rem, 5vw, 3.5rem);
        font-weight: 800;
        background: linear-gradient(135deg, var(--primary), var(--secondary));
        -webkit-background-clip: text;
        -webkit-text-fill-color: transparent;
        background-clip: text;
        margin-bottom: 16px;
        letter-spacing: -0.02em;
      }

      .subtitle {
        font-size: clamp(1rem, 2vw, 1.25rem);
        color: var(--text-secondary);
        max-width: 600px;
        margin: 0 auto;
      }

      /* Stats Bar */
      .stats-bar {
        display: flex;
        justify-content: center;
        gap: 40px;
        margin-top: 40px;
        flex-wrap: wrap;
        animation: fadeIn 1s ease-out 0.3s backwards;
      }

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

      .stat-number {
        font-size: 2rem;
        font-weight: 700;
        color: var(--primary);
        display: block;
      }

      .stat-label {
        font-size: 0.875rem;
        color: var(--text-secondary);
        text-transform: uppercase;
        letter-spacing: 0.05em;
      }

      /* Topics Grid */
      .topics-grid {
        display: grid;
        grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
        gap: 24px;
        list-style: none;
        margin-top: 40px;
      }

      .topic-card {
        background: var(--surface);
        border-radius: 16px;
        padding: 32px;
        cursor: pointer;
        transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
        border: 1px solid rgba(255, 255, 255, 0.05);
        position: relative;
        overflow: hidden;
        animation: fadeInUp 0.6s ease-out backwards;
      }

      .topic-card::before {
        content: '';
        position: absolute;
        top: 0;
        left: 0;
        right: 0;
        height: 4px;
        background: linear-gradient(90deg, var(--primary), var(--secondary));
        transform: scaleX(0);
        transform-origin: left;
        transition: transform 0.3s ease;
      }

      .topic-card:hover {
        transform: translateY(-8px);
        background: var(--surface-hover);
        box-shadow: 0 20px 40px var(--shadow-hover);
        border-color: rgba(61, 220, 132, 0.2);
      }

      .topic-card:hover::before {
        transform: scaleX(1);
      }

      .topic-card:nth-child(1) { animation-delay: 0.1s; }
      .topic-card:nth-child(2) { animation-delay: 0.2s; }
      .topic-card:nth-child(3) { animation-delay: 0.3s; }
      .topic-card:nth-child(4) { animation-delay: 0.4s; }
      .topic-card:nth-child(5) { animation-delay: 0.5s; }
      .topic-card:nth-child(6) { animation-delay: 0.6s; }

      .topic-header {
        display: flex;
        align-items: center;
        gap: 12px;
        margin-bottom: 16px;
      }

      .topic-icon {
        font-size: 2rem;
        filter: drop-shadow(0 2px 8px rgba(61, 220, 132, 0.3));
        transition: transform 0.3s ease;
      }

      .topic-card:hover .topic-icon {
        transform: scale(1.1) rotate(5deg);
      }

      .topic-number {
        font-size: 0.875rem;
        font-weight: 700;
        color: var(--primary);
        background: rgba(61, 220, 132, 0.1);
        padding: 4px 10px;
        border-radius: 8px;
        min-width: 32px;
        text-align: center;
      }

      .topic-text {
        font-size: 1.5rem;
        font-weight: 700;
        color: var(--text-primary);
        flex: 1;
      }

      .topic-description {
        color: var(--text-secondary);
        font-size: 0.9375rem;
        line-height: 1.6;
        margin-bottom: 16px;
      }

      .topic-footer {
        display: flex;
        align-items: center;
        justify-content: space-between;
        margin-top: 20px;
        padding-top: 16px;
        border-top: 1px solid rgba(255, 255, 255, 0.05);
      }

      .difficulty {
        display: inline-flex;
        align-items: center;
        gap: 6px;
        font-size: 0.75rem;
        font-weight: 600;
        padding: 6px 12px;
        border-radius: 20px;
        text-transform: uppercase;
        letter-spacing: 0.05em;
      }

      .difficulty.beginner {
        background: rgba(61, 220, 132, 0.15);
        color: var(--primary);
      }

      .difficulty.intermediate {
        background: rgba(255, 193, 7, 0.15);
        color: #ffc107;
      }

      .difficulty.advanced {
        background: rgba(244, 67, 54, 0.15);
        color: #f44336;
      }

      .arrow-icon {
        color: var(--primary);
        transition: transform 0.3s ease;
        font-size: 1.25rem;
      }

      .topic-card:hover .arrow-icon {
        transform: translateX(4px);
      }

      /* Search Bar */
      .search-container {
        max-width: 600px;
        margin: 0 auto 40px;
        position: relative;
        animation: fadeIn 1s ease-out 0.2s backwards;
      }

      .search-input {
        width: 100%;
        padding: 16px 48px 16px 20px;
        background: var(--surface);
        border: 2px solid rgba(255, 255, 255, 0.05);
        border-radius: 12px;
        color: var(--text-primary);
        font-size: 1rem;
        transition: all 0.3s ease;
      }

      .search-input:focus {
        outline: none;
        border-color: var(--primary);
        box-shadow: 0 0 0 3px rgba(61, 220, 132, 0.1);
      }

      .search-icon {
        position: absolute;
        right: 16px;
        top: 50%;
        transform: translateY(-50%);
        color: var(--text-secondary);
        font-size: 1.25rem;
      }

      /* Animations */
      @keyframes fadeIn {
        from {
          opacity: 0;
        }
        to {
          opacity: 1;
        }
      }

      @keyframes fadeInUp {
        from {
          opacity: 0;
          transform: translateY(30px);
        }
        to {
          opacity: 1;
          transform: translateY(0);
        }
      }

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

      /* Responsive */
      @media (max-width: 768px) {
        .container {
          padding: 40px 16px;
        }

        .topics-grid {
          grid-template-columns: 1fr;
          gap: 16px;
        }

        .stats-bar {
          gap: 24px;
        }

        .topic-card {
          padding: 24px;
        }
      }

      /* Loading State */
      .loading {
        opacity: 0.5;
        pointer-events: none;
      }

      /* Scroll Indicator */
      .scroll-indicator {
        position: fixed;
        top: 0;
        left: 0;
        height: 3px;
        background: linear-gradient(90deg, var(--primary), var(--secondary));
        z-index: 1000;
        transition: width 0.1s ease;
      }