body {
    margin-left: 15%;
    margin-right: 15%
    }
h1, h3 {
    text-align: center
    }
h2, h4 {
    margin-left: 5%
    }
hr {
    width: 50%;
    margin-top: 2em;
    margin-bottom: 1em
    }
.toc, .pic {
    font-size: 80%;
    text-align: center
    }