body {
  background-color: chocolate;
  counter-reset: section;
}

h1 {
  counter-reset: subsection;
}

h2::before {
  counter-increment: section;
  content: "Título Principal " counter(section) ": ";
  display: inline-block;
  margin-right: 5px;
}

h3::before {
  counter-increment: subsection;
  content: counter(section) "." counter(subsection) " ";
  display: inline-block;
  margin-right: 5px;
}

ol {
  counter-reset: section;
  list-style-type: none;
}

li::before {
  counter-increment: section;
  content: counters(section,".") " ";
}