.pswp__form-windows-container {
    position: relative;
    width: 100%;
    height: 100%;
    pointer-events: none;
}
.pswp__form-windows-container iframe {
    background: #444;
    width: 100%;
    height: 100%;
    max-width: 800px;
    max-height: 600px;
    pointer-events: auto;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}