html {
  font-size: 10px;
  background: url(https://wallpaperstock.net/wallpapers/thumbs1/47523wide.jpg);
  background-size: cover;
  min-height: 100vh;
}

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

.keys {
  display: flex;
  flex: 1;
  min-height: 90vh;
  align-items: center;
  justify-content: center;
}

.key {
  border: 0.4rem solid red;
  border-radius: 0.5rem;
  margin: 1rem;
  font-size: 1.5rem;
  padding: 1rem 0.5rem;
  transition: all 0.7s ease;
  width: 100px;
  text-align: center;
  color: white;
  background: rgba(243, 64, 64, 0.4);
  text-shadow: 0 0 0.5rem black;
}

.playing {
  transform: scale(1.1);
  border-color: #ffc600;
  box-shadow: 0 0 1rem #ffc600;
}

kbd {
  display: block;
  font-size: 40px;
}

.sound {
  font-size: 1.2rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: #ffc600;
  font-weight: bolder;
}