html {
  font-size: 10px;
}

body {
  background: url("https://img00.deviantart.net/818c/i/2018/167/3/2/piano_lesson_by_silverbloodwolf98-dced6p5.jpg") center;
  background-size: cover;
  margin: 0;
  padding: 0;
  font-family: sans-serif;
}

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

.key {
  border: 0.2em solid black;
  border-radius: 0.5em;
  margin: 0.3em;
  font-size: 1.5em;
  padding: 1em 0.5em;
  transition: all 0.07s ease;
  height: 30em;
  width: 50em;
  text-align: center;
  color: white;
  background: rgba(0,0,0,0.4);
  text-shadow: 0 0 0.5em black;
}

.music {
  transform: scale(1.1);
  border-color: #e5ff00;
  box-shadow: 0 0 2em #e5ff00;
}

kbd {
  display: block;
  font-size: 2.5em;
  text-align: center;
}

.sound {
  font-size: 1.5em;
  color: #c1e61c;
    
}