body {
    counter-reset: h1
}

h1 {
    counter-set: h2 0;
}

h2 {
    counter-set: h3 0;
}

h3 {
    counter-set: h4 0;
}

h1:before {
    counter-increment: h1;
}

h2:before {
    content: counter(h2) ". ";
    counter-increment: h2;
}

h3:before {
    content: counter(h2) "." counter(h3) ". ";
    counter-increment: h3;
}

h4:before {
    content: counter(h2) "." counter(h3) "." counter(h4) ". ";
    counter-increment: h3;
}

details {
    margin-left: 0.5rem;
    padding-left: 0.5rem;
}

details.callout-card {
    border-left: 1px solid grey;
}

summary {
    margin-bottom: .5rem;
}