.gallery .lightbox {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0,0,0,0.8);
    z-index: 9999;
    display: none;
}

.gallery .lightbox img {
    max-width: 90%;
    max-height: 90%;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}