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

@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 {
    display: flex;
    flex-wrap: wrap;
    list-style-type: none;
    font-size: 0.8rem;
    padding: 0;
}

#fixed-size-grid-items ul li {
    display: block;
}

#fixed-size-grid-items ul li aside {
    width: 170px;
    margin: 10px;
}

#stretchable-grid-items ul {
    display: flex;
    flex-wrap: wrap;
    padding: 0;
    list-style-type: none;
    font-size: 0.8rem;
    margin: 1rem -10px;
}

#stretchable-grid-items ul li {
    width: 100%;
    display: block;
}

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

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

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