* {
  margin: 0;
  padding: 0;
  font-size: 10px;
}
.keys {
  background: url("img/background.jpeg") center center/cover no-repeat;

  display: flex;
  min-height: 100vh;
  justify-content: center;
  align-items: center;
}

.key {
  border: 0.4rem solid black;
  border-radius: 0.5rem;
  color: white;
  margin: 1rem;
  font-size: 4rem;
  padding: 1rem 0.5rem;
  text-align: center;
  width: 10rem;
  background: rgba(0, 0, 0, 0.4);
  transition: all 0.07s;
}
.playing {
  transform: scale(1.1);
  border-color: #ffc600;
  box-shadow: 0 0 1rem #ffc600;
}

.key span {
  color: gold;
  display: block;
  font-size: 1.2rem;
  text-transform: uppercase;
  letter-spacing: 0.1rem;
}