main {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    grid-auto-rows: 150px;
}

main div {
    height: 100%;

    display: flex;
    align-items: center;
    justify-content: center;

    /* default color */
    background: #aaa;
}

main a {
    color: inherit;
}