@media (min-width: 40em) {
    main {
        width: 80%;
        justify-self: center;
    }

    main #photos {
        display: grid;
        grid-template-columns: repeat(4, auto);
        justify-content: space-around;
        width: 100%;
    }

    #photos > * {
        height: 100%;
    }

    #photos img.portrait {
        height: 60vh;
        filter: grayscale(0.5);
        transition: filter 1s, transform 1s;
    }

    #photos img.portrait:hover {
        filter: none;
        transform: scale(1.05);
    }
}

@media (max-width: 40em) {
    #photos {
        display: grid;
        grid-template-columns: repeat(4, 20%);
        justify-content: space-evenly;
        width: 100%;
    }

    #photos > * {
        width: 100%;
        height: 50vh;
    }

    #photos img.portrait {
        width: 100%;
        height: 100%;
        object-fit: cover;
        object-position: center;
    }
}