style.css

html {
  height: 100%;
  background: url("images/background.jpg") bottom center;
  background-size: cover;
  color: rgba(255, 255, 255, 0.75);
}

body {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-wrap: wrap;
  font-family: monospace;
  overflow: hidden;
  user-select: none;
}

.keys {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: center;
}
.key {
  margin: 0.5rem 1rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  width: 6rem;
  aspect-ratio: 1;
  padding: 1rem;
  border: 0.25rem solid rgba(255, 255, 255, 0.75);
  background: rgba(0, 0, 0, 0.025);
  transition: all 0.075s ease;
  box-shadow: 0 0 0.255rem black;
}
kbd {
  font-size: 2rem;
}

.sound {
  font-size: 1.25rem;
  color: #df86b1;
}
.playing {
  transform: scale(1.1);
  border-color: #bb1c69;
  box-shadow: 0 0 1rem #bb1c69;
}