html {
  background-image: url("https://i.pinimg.com/originals/51/bc/09/51bc0996c7a74ff83b9b2dfc24a45b7f.jpg");
  background-size: cover;
}

body, html {
  margin: 0;
  padding: 0;
  font-family: sans-serif;
}

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

.key {
  border: 4px solid black;
  border-radius: .5rem;
  font-size: 40px;
  color: white;
  transition: all .07s ease;
  font-weight: bold;
  text-align: center;
  margin-right: 20px;
  background: rgba(0, 0, 0, 0.4);
  text-shadow: 0 0 5px black;
}

.key kbd {
  padding: 35px;
}

.sound {
  display: block;
  font-size: 17px;
  color: #ffcc00;
  font-weight: bold;
  text-transform: uppercase;
}

.playing {
  transform: scale(1.1);
  border-color: #ffc600;
  box-shadow: 0 0 10px #ffc600;
}