.portfolio-box img {
    height: 400px;
    width: 100%;
    object-fit: cover;
    object-position: center;
}

.portfolio-box:hover .overlay {
    opacity: 1;
    transition: all 0.3s ease-out;
}

@media (max-width: 991.98px) {
    .portfolio-box img {
        height: 400px;
    }  
}

@media (max-width: 767.98px) {
    .portfolio-box img {
        height: 350px;
    }
}

@media (max-width: 575.98px) {
    .portfolio-box img {
        height: 250px;
    }
}