html {
  font-size: 10px;
  background: url(https://images.unsplash.com/photo-1557128928-66e3009291b5?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9) bottom center;
  background-size: cover;
}

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

.instructions {
  text-align: center;
  font-size: 2.5rem;
  margin: auto;
  margin-top: 100px;
  border: grey solid;
  width: 60%;
  background: whitesmoke;
}

.keys {
  display: flex;
  flex: 1;
  min-height: 100vh;
  align-items: center;
  justify-content: center;
}

.key {
  border: .4rem solid black;
  border-radius: .5rem;
  margin: 1rem;
  font-size: 1.5rem;
  padding: 1rem .5rem;
  transition: all .07s ease;
  width: 10rem;
  text-align: center;
  color: white;
  background: rgba(0, 0, 0, 0.4);
  text-shadow: 0 0 .5rem black;
}

.playing {
  transform: scale(1.5);
  border-color: #ffc600;
  box-shadow: 0 0 1rem orange;
  background: url(https://images.unsplash.com/photo-1557128928-66e3009291b5?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9);
  background-size: cover;
}

kbd {
  display: block;
  font-size: 4rem;
}

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