body {
    width: 90%;
    margin: 5% auto;
    left: 0;
    right: 0;
    font-family: georgia, serif;
    line-height: 32px;
    font-size: 18px;
}

h1 {
    font-size: 36px;
    line-height: 42px;
    margin: 16px 0;
}
h2 {
    font-size: 1.2em;
    margin: 16px 0;
}

img {
    width: 100%;
}

table {
    width: 100%;
    border-collapse: collapse;
}
td, th {
    padding: 1em;
    border: 1px solid lightgrey;
}

@media (min-width: 640px) {
    
    body {
        width: 600px;
        margin: 2em auto;
    }
}