.popup-overlay {
      position: fixed;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background-color: rgba(0, 0, 0, 0.5);
      z-index: 999;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    /* Pop-up venster */
    .popup-message {
      background-color: #fff;
      padding: 30px 20px;
      max-width: 400px;
      text-align: center;
      border-radius: 12px;
      box-shadow: 0 4px 15px rgba(0,0,0,0.3);
      font-family: sans-serif;
      position: relative;
    }

    /* Sluitknop */
    .close-btn {
      position: absolute;
      top: 8px;
      right: 12px;
      background: none;
      border: none;
      font-size: 20px;
      cursor: pointer;
    }