body {
    max-width: 800px;
    width: 90%;
}

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

@media (min-width: 640px) {
    html {background-color: #eaf6ff;}
    h1 {font-size: 2.5rem;}
}

#fixed-size-grid-items ul {
    display: flex;
    flex-wrap: wrap;
    box-sizing: border-box;
    font-size: 0.8rem;
    list-style-type: none;
    float: inline-start;
}

aside {margin: 10px;}

#fixed-size-grid-items aside {
    width: 170px;
    padding-left: none;
}

#stretchable-grid-items ul {
    display: flex;
    flex-wrap: wrap;
    box-sizing: border-box;
    font-size: 0.8rem;
    list-style-type: none;
    float: inline-start;
    margin-left: -10px;
    margin-right: -10px;
    margin-top: 1rem;
    margin-bottom: 1rem;
}

@media (max-width: 479px) {
#stretchable-grid-items li {
    width: 100%;
    padding-left: none;}
}

@media (min-width: 480px) {
    #stretchable-grid-items li {
        width: 50%;}
}

@media (min-width: 640px) {
    #stretchable-grid-items li {
        width: 25%;}
}