.custom-overlay{
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    background-color: rgba(0,0,0,0.6);
    overflow: hidden;
    width: 100%;
    height: 0;
    transition: .2s ease;
}
  
.portfolio-info:hover .custom-overlay {
    height: 100%;
}