riff_site/output/assets/css/nikola_rst.css

div.admonition, div.attention, div.caution, div.danger, div.error,
div.hint, div.important, div.note, div.tip, div.warning, div.sidebar,
div.system-message {
/* stolen from Boostrap 4 (.card) */
  margin-bottom: 2rem;
  position: relative;
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-orient: vertical;
  -webkit-box-direction: normal;
  -ms-flex-direction: column;
  flex-direction: column;
  min-width: 0;
  word-wrap: break-word;
  background-color: #fff;
  color: #212529;
  background-clip: border-box;
  border: 1px solid rgba(0,0,0,.125);
  border-radius: .25rem;
  padding: 0;
}

div.attention, div.caution, div.danger, div.error, div.warning {
  /* stolen from Boostrap 3 (.border-danger) */
  border-color: #dc3545!important;
}

div.admonition p, div.hint p,
div.important p, div.note p,
div.tip p, div.sidebar p,
div.attention p, div.caution p,
div.danger p, div.error p,
div.warning p, div.system-message p {
    padding-left: 1rem;
    padding-right: 1rem;
}

div.admonition p.admonition-title, div.hint p.admonition-title,
div.important p.admonition-title, div.note p.admonition-title,
div.tip p.admonition-title, div.sidebar p.sidebar-title,
div.attention p.admonition-title, div.caution p.admonition-title,
div.danger p.admonition-title, div.error p.admonition-title,
div.warning p.admonition-title, div.system-message p.system-message-title {
/* stolen from Boostrap 4 (.card .card-header) */
  font-weight: 400;
  font-size: 1.25rem;
  padding: .75rem 1.25rem;
  margin-bottom: 1rem;
  background-color: rgba(0,0,0,.03);
  border-bottom: 1px solid rgba(0,0,0,.125);
}

div.attention p.admonition-title, div.caution p.admonition-title,
div.danger p.admonition-title, div.error p.admonition-title,
div.warning p.admonition-title, div.system-message p.system-message-title {
  /* stolen from Boostrap 4 (.card .card-header .bg-danger) */
  background-color: #dc3545;
  color: white;
}

div.sidebar {
    margin-right: 0;
}

/* Improved margin overrides */
div.topic,
pre.literal-block,
pre.doctest-block,
pre.math,
pre.code,
div.code {
    margin-left: 1rem;
    margin-right: 1rem;
}

div.code {
    margin-bottom: 1rem;
}