body {
  text-align: center;
}

.keys {
  font-weight: bold;
  font-size: 9em;
  font-family: monospace;
  color: grey;
}
.keys :nth-child(3) {
  color: black;
}
.keys img {
  opacity: 0.5;
}
.keys :nth-child(3) img{
  opacity: 1;
}
.control {
  padding: 1em;
  margin: 0.5em;
}
.keyform {
  text-align: left;
}
details > p {
  text-align: justify;
}
details > summary {
  font-size: big;
  font-weight: bold;
}