article {
    // Named after the LaTeX counters after `chapter` counter.
    counter-reset: section subsection subsubsection paragraph subparagraph;
    --counter-spacing: 0.5rem;

    // <h2> is used as a section header since <h1> is the main title
    h2 {
        counter-reset: subsection;
        counter-increment: section;

        &::before {
            content: counter(section) ".";
            margin-right: var(--counter-spacing);
        }
    }

    h3 {
        counter-reset: subsubsection;
        counter-increment: subsection;

        &::before {
            content: counter(section) "." counter(subsection) ".";
            margin-right: var(--counter-spacing);
        }
    }

    h4 {
        counter-reset: paragraph;
        counter-increment: subsubsection;

        &::before {
            content: counter(section) "." counter(subsection) "." counter(subsubsection) ".";
            margin-right: var(--counter-spacing);
        }
    }

    h5 {
        counter-reset: subparagraph;
        counter-increment: paragraph;

        &::before {
            content: counter(section) "." counter(subsection) "." counter(subsubsection) "." counter(paragraph) ".";
            margin-right: var(--counter-spacing);
        }
    }

    h6 {
        counter-increment: subparagraph;

        &::before {
            content: counter(section) "." counter(subsection) "." counter(subsubsection) "." counter(paragraph) "." counter(subparagraph);
            margin-right: var(--counter-spacing);
        }
    }
}