.gallery-thumbnail-image-column {
    margin-top: 15px;
    margin-bottom: 15px;
}

.gallery-thumbnail-image-grid img {
    max-width: 100%;
    max-height: 100%;
}

.gallery-thumbnail-image-grid:hover .gallery-thumbnail-enlarge,
.gallery-thumbnail-image-grid:focus .gallery-thumbnail-enlarge {
    top: 50%;
}

.gallery-thumbnail-image-grid:hover .gallery-thumbnail-enlarge,
.gallery-thumbnail-image-grid:focus .gallery-thumbnail-enlarge,
.gallery-thumbnail-image-grid:hover .gallery-thumbnail-overlay,
.gallery-thumbnail-image-grid:focus .gallery-thumbnail-overlay {
    opacity: 1;
}

.gallery-thumbnail-enlarge {
    position: absolute;
    top: 60%;
    left: 50%;
    transform: translate(-50%,-50%);
    color: #ffffff;
    z-index: 1;
    width: 100%;
    text-align: center;
    opacity: 0;
    padding: 1em;
    transition: opacity .6s ease, top .6s ease;
}

.gallery-thumbnail-overlay {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    background-color: rgba(0,0,0,.6);
    opacity: 0;
    transition: opacity .6s ease;
}