.image-mosaic { display: grid; gap: 1rem; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); grid-auto-rows: 210px; }
.image-mosaic .shadow { background: #000; width: 100%; height: 100%; opacity: 0; }
.image {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    height: 100%;
    width: 100%;
    transition: all 500ms;
    overflow: hidden;
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    padding: 0;
    margin: 0;
}
.image:hover .shadow { opacity: 30%; }
@media screen and (min-width: 600px) {
    .tall { grid-row: span 2 / auto; }
    .wide { grid-column: span 2 / auto; }
}