style.css

body {
    background: #fff;
    color: #000;
    font-size: 1ex;
    counter-reset: part-number chapter-number index-part-number index-number;
}

#contents {
    text-align: center;
    border-bottom: 1px solid;
    margin-bottom: 20px;
}

#contents + ul li {
    list-style-type: none;
}

#contents + ul p a {
    counter-increment: index-part-number;
}

#contents + ul p a::before {
    content: "Part " counter(index-part-number, upper-roman) " - ";
}

#contents + ul ul a {
    counter-increment: index-number;
}

#contents + ul ul a::before {
    content: counter(index-number)". ";
}

h1 {
    page-break-before: always !important;
    padding-top: 100px;
    text-align: center;
    font-weight: bold;
    font-size: 4ex;
    counter-increment: part-number;
}

h1::before {
    content: "Part " counter(part-number, upper-roman);
    display: block;
    margin-bottom: 120px;
}

h2 {
    page-break-before: always !important;
    font-weight: bold !important;
    font-size: 2ex !important;
    counter-increment: chapter-number;
}

h2::before {
    content: counter(chapter-number);
    margin-right: 10px;
}

hr {
    border: 1px black;
    border-top: double;
    width: 50%;
    text-align: center;
}

.index-title {
    text-align: center;
    font-weight: bold;
    font-size: 2ex;
}

.index-divider {
    margin-left: 20px;
    width: 90%;
    border: 1px solid black;
}

a {
    text-decoration: none
}