li::before {
  display:inline-block;
  width: 1rem;
  height: 1rem;
  margin-right: 0.25rem;
  content:"";
}

#head {
  font-size: 18px;
}

.open::before, .closed::before {
  background-size: 1rem 1rem;
  position: relative;
  top: 0.25rem;
  opacity: 0.3;
}

.closed .closed::before, .closed .open::before {
  display: none;
}

#container {
  border: 1px solid black;
  padding: 5px;
  margin-right: 10px;
}

.closed #body {
  display: none;
}