body {
      font-family: Arial, sans-serif;
    }

    /* Styl miniatury */
    .thumbnail {
      width: 200px;
      cursor: pointer;
      transition: 0.3s;
    }

    .thumbnail:hover {
      opacity: 0.8;
    }

    /* Styl okna popup */
    .popup {
      display: none; /* ukryte domyślnie */
      position: fixed;
      z-index: 1000;
      padding-top: 50px;
      left: 0;
      top: 0;
      width: 100%;
      height: 100%;
      overflow: auto;
      background-color: rgba(0,0,0,0.8);
    }

    .popup-content {
      margin: auto;
      display: block;
      max-width: 90%;
      max-height: 90%;
      border-radius: 10px;
      box-shadow: 0 0 10px #fff;
    }

    .close-btn {
      position: absolute;
      top: 20px;
      right: 40px;
      color: #fff;
      font-size: 40px;
      font-weight: bold;
      cursor: pointer;
    }