html,body{
    width:100%;
    height:100%;
    margin:0;
    padding:0;
    color:#222;
    line-height:1.5rem;
}
#center{
    max-width:48em;
    margin:0 auto;
    padding:1em;
}
.code{
    background-color:#222;
    color:#eee;
    padding:1em;
    margin:1em 0;
}
img{
    width:80%;
    display:block;
    margin:1em;
}

table {
    border-collapse:  collapse;
}

th,td{
    padding: 0.5em;
    border: 0.1em solid #222;
}

@media screen and (max-width: 640px) {
    body{
        font-size:0.9rem;
    }
}