counter.css

body {
  font-size: 1rem;
  margin: 0 auto;
  width: 40%;
  font-family: 'Cormorant Infant', serif;
  counter-reset: heading;
}

.overview {
  height: 100vh;
  font-size: 30px;
  counter-reset: chapter;
}

.overview h3 {
  text-decoration: underline;
}

.overview h4::before {
  counter-increment: chapter;
  content: "Chapter " counter(chapter) ":  ";
}

.overview h4 {
  margin-left: 40px;
  counter-reset: subchapter;
}

.overview h6::before {
  margin-left: 60px;
  counter-increment: subchapter;
  content: counter(chapter) "." counter(subchapter) ")";
}

h1::before {
  counter-increment: heading;
  content: "Chapter " counter(heading) ": ";
  font-weight: bold;
  text-decoration: underline;
}

p {
  height: 100vh;
  line-height: 3.5;
}

p.chapter-1:first-letter {
  font-size: 100px;
  line-height: 1;
  margin: 15px 15px 10px 0px;
  display: block;
  float: left;
}