body {
    width: 90%;
    margin: auto;
}

#fixed-size-grid-items li {
    padding: 0;
    margin: 10px;
    list-style-type: none;
}
#fixed-size-grid-items ul {
    padding-left: 0;
    font-size: 0.8rem;
    display: grid;
    grid-template-columns: repeat(auto-fill, 170px);
}

#stretchable-grid-items li {
    width: 100%;
    list-style-type: none;
}

#stretchable-grid-items ul {
    padding-left: 0;
    font-size: 0.8rem;
    display: grid; 
    grid-template-columns: repeat(2, 50%);
}

@media (max-width: 500px) {
    h1 {
        font-size: 1.5rem;
    }
    #stretchable-grid-items ul {
        display: grid; 
        grid-template-columns: repeat(1, 100%)
    }
}

@media (min-width: 640px) {
    body {
        background-color: #eaf6ff;
    }
    h1 {
        font-size: 2.5rem;
    }
    #stretchable-grid-items ul {
        display: grid;
        grid-template-columns: repeat(4, 25%);
    }
}