*:focus {
  outline: 2px dotted black;
}

.visually-hidden {
  position: absolute;
  margin: -1px;
  border: 0;
  padding: 0;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
}

.accordion:focus-within .header label {
  background-color: #ffffb3;
}

.header h2 {
  margin-bottom: 0;
}
.header label {
  display: block;
  border: 1px solid black;
  margin: 0 0 -1px 0;
  padding: 4px 10px;
  background-color: lightyellow;
}
.header label::before {
  content: "+";
  display: inline-block;
  width: 0.75em;
  font-weight: normal;
}

input[type="radio"]:checked + h2 label {
  border-bottom-color: lightyellow;
  position: relative;
}
input[type="radio"]:checked + h2 label::before {
  content: "-";
}

.accordion a:focus,
.accordion input:focus,
.accordion input[type="radio"]:focus + h2 label {
  outline: 2px dotted red;
  outline-offset: 2px;
}

input[type="radio"] + h2 label:hover {
  cursor: pointer;
  text-decoration: underline;
}

.panel {
  border: 1px solid;
  background-color: lightyellow;
  padding: 0 0 0 10px;
}
