.collapsible-section div.collapse-button::before {
  background-image: url("data:image/svg+xml;utf8,<svg fill='currentColor' height='16' viewBox='0 0 16 16' width='16' xmlns='http://www.w3.org/2000/svg'><path d='M12.25,6h-7.5C3.788,6,3.532,6.581,4.183,7.29l3.304,3.604c0.558,0.607,1.47,0.607,2.027,0l3.304-3.604 C13.468,6.581,13.213,6,12.25,6z'/></svg>");
  content: "";
  font-family: monospace;
  height: 16px;
  margin-right: 4px;
  transition: all 0.35s ease-in-out;
  width: 16px;
  display: inline-block;
  transform: rotate(-90deg);
}

.collapsible-section div.collapse-button[aria-expanded="true"]::before {
  transform: rotate(0deg);
}