.sentences-display {
  width: 50%;
  height: 100%;
  margin: 0 0 1em auto;
  padding: 5px;
  overflow: hidden;
  color: grey;
  font-size: 2rem;
  white-space: nowrap;
  background-color: #fff;
  border: 1px solid #ccc;
  border-radius: 5px;
}

.sentences-display::first-letter {
  color: black;
}

.key {
  display: inline-block;
  min-width: 5%;
  height: 1.5em;
  margin: 0.1em;
  padding-top: 0.1em;
  color: #000;
  font-weight: bold;
  font-weight: 400;
  font-size: 1.5em;
  text-align: center;
  background-color: #fff;
  border: 1px solid #000;
  border-radius: 3px;
  cursor: pointer;
}

.key.active {
  color: #fff;
  background-color: green;
}

section {
  width: 50%;
  margin: 1rem auto;
  color: #000;
  font-weight: bold;
  font-size: 2rem;
  text-align: center;
}