:root {
  --section-prefix: '';
}

main :is(h1, h2, h3, h4, h5, h6):not(.unnumbered)::before {
  padding-right: 1ex;
}

main h1:not(.unnumbered) { counter-increment: h1; }
main h1 { counter-reset: h2 h3 h4 h5 h6; }
main h1:not(.unnumbered)::before {
  content: var(--section-prefix) counter(h1);
}

main h2:not(.unnumbered) { counter-increment: h2; }
main h2:not(.unnumbered)::before {
  content: var(--section-prefix) counter(h1) '.' counter(h2);
}
main h2 { counter-reset: h3 h4 h5 h6; }

main h3:not(.unnumbered) { counter-increment: h3; }
main h3 { counter-reset: h4 h5 h6; }
main h3:not(.unnumbered)::before {
  content: var(--section-prefix) counter(h1) '.' counter(h2) '.' counter(h3);
}

main h4:not(.unnumbered) { counter-increment: h4; }
main h4 { counter-reset: h5 h6; }
main h4:not(.unnumbered)::before {
  content: var(--section-prefix)
    counter(h1) '.' counter(h2) '.' counter(h3) '.' counter(h4);
}

main h5:not(.unnumbered) { counter-increment: h5; }
main h5 { counter-reset: h6; }
main h5:not(.unnumbered)::before {
  content: var(--section-prefix)
    counter(h1) '.' counter(h2) '.' counter(h3) '.' counter(h4) '.'
    counter(h5);
}

main h6:not(.unnumbered) { counter-increment: h6; }
main h6:not(.unnumbered)::before {
  content: var(--section-prefix)
    counter(h1) '.' counter(h2) '.' counter(h3) '.' counter(h4) '.'
    counter(h5) '.' counter(h6);
}