body{
    font-family: "Roboto", sans-serif;
}
header, main, footer {
    max-width: 640px;
    margin: 1em auto;
    border: 1px solid #ccc;
    padding: 1em;
    background-color: aqua;
    
}

main{
    display:grid;
    grid-template-columns: 1fr;
    grid-gap: 1rem;
}
section{
    background-color: white;
    padding: 1em;
}
@media screen and (min-width: 500px)
{
    main{
        grid-template-columns: 1fr 1fr;
    }
    header{
        background-color: #333;
        color: white;
    }
}