:root {
      --primary-color: #007bff;
      --shadow: 0 2px 5px rgba(0,0,0,0.2);
      --transition: all 0.3s ease;
    }

    .navbar {
      background-color: #333;
      overflow: hidden;
      padding: 10px 0;
      text-align: center;
      margin-bottom: 10px;
    }

    .navbar-title {
      color: white;
      font-size: 24px;
      font-weight: bold;
      margin-bottom: 10px;
    }

    .navbar-menu {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 10px;
      max-width: 800px;
      margin: 0 auto;
      justify-items: center;
    }

    .navbar a {
      display: block;
      color: white;
      text-align: center;
      padding: 14px 20px;
      text-decoration: none;
      font-size: 18px;
      background-color: #444;
      border-radius: 8px;
      width: 100%;
      max-width: 150px;
      transition: var(--transition);
    }

    .navbar a:hover {
      background-color: #555;
      transform: translateY(-2px);
      box-shadow: var(--shadow);
    }

    .navbar a.active {
      background-color: var(--primary-color);
    }

    .content {
      padding: 20px;
    }

    body {
      font-family: system-ui, -apple-system, Arial, sans-serif;
      max-width: 1200px;
      margin: 0 auto;
      padding: 20px;
      background-color: #f5f5f5;
    }

    nav, .section {
      margin-bottom: 40px;
    }

    .menu {
      display: flex;
      flex-wrap: wrap;
      gap: 10px;
    }

    .menu a {
      flex: 1 1 200px;
      padding: 12px 20px;
      background-color: #f0f0f0;
      color: #333;
      border: 1px solid #ddd;
      border-radius: 8px;
      text-align: center;
      text-decoration: none;
      font-size: 14px;
      transition: var(--transition);
    }

    .menu a:hover {
      background-color: var(--primary-color);
      color: white;
      transform: translateY(-2px);
      box-shadow: var(--shadow);
    }

    .menu a:active {
      transform: translateY(0);
      box-shadow: none;
    }

    @media (max-width: 600px) {
      .navbar-menu {
        grid-template-columns: repeat(4, 1fr);
        gap: 5px;
      }
      .navbar a {
        max-width: 100%;
        padding: 10px;
        font-size: 16px;
      }
      .menu {
        display: grid;
        grid-template-columns: repeat(2, 1fr);
        gap: 10px;
      }
      .menu a {
        flex: none;
        width: auto;
      }
    }

    h2 {
      color: #444;
      border-bottom: 2px solid #ddd;
      padding-bottom: 10px;
    }

    .grid {
      display: flex;
      flex-wrap: wrap;
      gap: 8px;
      margin-bottom: 10px;
    }

    .cell {
      width: 50px;
      height: 50px;
      display: flex;
      justify-content: center;
      align-items: center;
      border: 1px solid #ccc;
      border-radius: 5px;
      background-color: #fff;
      font-size: 24px;
      transition: transform 0.2s, box-shadow 0.2s;
      cursor: pointer;
    }

    .cell:hover {
      transform: scale(1.2);
      box-shadow: var(--shadow);
    }

    .to-top {
      position: fixed;
      bottom: 120px;
      right: 20px;
      background-color: var(--primary-color);
      color: white;
      padding: 10px 15px;
      border-radius: 50%;
      font-size: 14px;
      text-decoration: none;
      box-shadow: var(--shadow);
      opacity: 0.7;
      transition: var(--transition);
      z-index: 1000;
      display: none;
    }

    .to-top.show {
      display: block;
    }

    .to-top:hover {
      opacity: 1;
      transform: translateY(-2px);
    }

    .to-top:active {
      transform: translateY(0);
    }