.gallery-card .overlay{
    background-color: rgba(0,0,0,.4);
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 0;
    transition: height .25s ease-in-out;
}
.gallery-card .overlay i{
    color: white;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-50%);
    opacity: 0;
    transition: opacity .25s ease-in-out;
}
.gallery-card:hover .overlay{
    height: 100%;
}
.gallery-card:hover .overlay i{
    opacity: 1;
    transition: opacity .25s ease-in-out .20s;
}