@media screen and (min-width: 800px) {
  body {
    max-width: min(90%, 800px);
  }
}

details>summary {
  list-style: none
}

details>summary::-webkit-details-marker,details>summary::marker {
  display: none
}

summary:before {
  border-bottom: 6px solid transparent;
  border-left: 10px solid var(--b-txt);
  border-top: 6px solid transparent;
  content: "";
  display: inline-block;
  height: 0;
  margin-right: 10px;
  position: relative;
  transition: .2s;
  width: 0
}

details[open] summary:before {
  transform: rotate(90deg)
}

h2, h3, h4, h5 {
  margin-top: 1.5em;
  margin-bottom: .6em;
}

@media screen and (max-width: 900px) {
  iframe {
    display: none;
  }
}