body {
      margin: 0;
      padding: 0;
      font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
      background: white;
      display: flex;
      justify-content: center;
      align-items: center;
      min-height: 100vh;
    }
    
    .ch4-card {
      background: white;
      border-radius: 20px;
      padding: 30px;
      box-shadow: inset 0 0 20px rgba(33, 150, 243, 0.15);
      text-align: center;
      min-width: 280px;
      max-width: 400px;
      border: 2px solid #90caf9;
    }
    
    .ch4-title {
      font-size: 18px;
      color: #616161;
      font-weight: 600;
      margin-bottom: 15px;
      text-transform: uppercase;
      letter-spacing: 1px;
    }
    
    .ch4-first-value {
      font-size: 16px;
      font-weight: 600;
      color: #616161;
      margin: 10px 0 5px 0;
    }
    
    .ch4-first-date {
      font-size: 13px;
      color: #9e9e9e;
      margin: 0 0 20px 0;
    }
    
    .ch4-current-value {
      font-size: 48px;
      font-weight: bold;
      color: #000000;
      margin: 15px 0 5px 0;
      line-height: 1;
    }
    
    .ch4-current-date {
      font-size: 14px;
      color: #9e9e9e;
      margin: 5px 0 15px 0;
    }
    
    .footer-copyright {
      margin-top: 20px;
      padding-top: 15px;
      border-top: 1px solid #e3f2fd;
      font-size: 10px;
      color: #9e9e9e;
      line-height: 1.4;
    }
    
    .footer-copyright a {
      color: #42a5f5;
      text-decoration: none;
      font-weight: 500;
    }
    
    .footer-copyright a:hover {
      text-decoration: underline;
    }
    
    /* Mobil optimalizálás */
    @media (max-width: 480px) {
      .ch4-card {
        padding: 20px;
        min-width: 240px;
      }
      
      .ch4-current-value {
        font-size: 40px;
      }
    }