html, body {
    height: 100%;
    margin: 0;
}

body {
    display: flex;
    flex-direction: column;
}

main {
    flex: 1;
}

.card-img-top {
    height: 12rem;
    object-fit: cover;
}

.carousel-item:after {
    content: "";
    display: block;
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    background: #000000;
    opacity: 0.4;
}

.carousel-caption {
    z-index: 2;
}

footer>div {
    position: relative;
    bottom: 0;
}