html {
  background: url(images/audience.jpg) no-repeat center center fixed;
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}
.sound {
  text-transform: uppercase;
}
kbd {
  display: block;
  font-size: 20px;
}
.key {
  border: 4px solid #000000;
  border-radius: 5px;
  margin: 16px;
  width: 80px;
  font-size: 15px;
  transition: all .07s;
  text-align: center;
  color: #FFFFFF;
  background: rgba(0,0,0,0.4);
  text-shadow: 0 0 5px #000000;
  display: inline-block;
}
.playing {
  transform: scale(1.1);
  border-color: #ffc600;
  box-shadow: 0 0 10px #ffc600;
}
.keys {
  position: fixed;
  top: 50%;
  left: 50%;
  margin-top: -150px;
  margin-left: -560px;
}