.at-article-flip-front, .at-article-flip-back {
    display: table;
    width: 100%;
    height: 100%;
    padding: 1em 0 1em 0;
    background: no-repeat center center;
    text-align: center;
}
.at-article-flip{
    position: relative;
}
.at-article-flip-front{
    position: relative;
    z-index: 1;
    transition: opacity 0.3s;
}

.at-article-flip-back {
    position: absolute;
    top: 0;
    left: 0;
    opacity: 1;
}

.at-article-flip-front::before, .at-article-flip-back::before {
    content: "";
    position: absolute;
    right: 0;
    bottom: 0;
    left: 0;
    top: 0;
}

.at-article-flip-front .at-af-contentContainer, .at-article-flip-back .at-af-contentContainer {
    position: relative; /** stack over transparent color*/
    display: table-cell;
    vertical-align: middle;
}