body {
    width: 90%;
    max-width: 800px;
    margin-left: auto; margin-right: auto;
}

@media (min-width: 640px) {
    html { background-color: #eaf6ff;

    }
}

@media (max-width: 500px) {
    h1 { font-size: 1.5rem;

    }
}

@media (min-width: 640px) {
    h1 { font-size: 2.5rem;

    }
}

#fixed-size-grid-items ul {
    list-style-type: none;
    padding-left: 0;
    display: grid;    
    grid-template-columns: repeat(auto-fit, minmax(170px , 1fr));
}

#fixed-size-grid-items aside {
    width: 170px;
    margin: 10px;
    font-size: 0.8rem;

}

#stretchable-grid-items ul {
    list-style-type: none;
    display: grid;
    padding-left: 0;
    margin: -10px, 1, -10px, 1;
}

@media (min-width: 480px) {
    #stretchable-grid-items ul {
        grid-template-columns: repeat(2, 1fr); 

    }
}

@media (min-width: 640px) {
    #stretchable-grid-items ul {
        grid-template-columns: repeat(4, 1fr); 
    }
}

#stretchable-grid-items aside {
    margin: 10px;
}