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

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

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

#fixed-size-grid-items ul {
    display: flex; 
    flex-wrap: wrap;
    list-style: none; 
    padding-left: 0px; 
}

#fixed-size-grid-items ul li aside {
    width: 170px; 
    margin: 10px; 
    font-size: .8rem; 

}

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

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

#stretchable-grid-items li{
    width: 100%; 
    font-size: 0.8rem; 
}

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

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