style.css

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  height: 10px;
}

body {
  background-image: url("https://images.unsplash.com/photo-1554324042-88b7823c4c43?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=1950&q=80");
  width: 100vw;
  height: 100vh;
}

.keys {
  min-width: 100vw;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  margin: 0 auto;
}

.key {
  height: 3rem;
  width: 3rem;
  color: lawngreen;
  padding: 2.4rem;
  margin: 0 1rem;
  transition: all 0.07s;
  border: 4px solid lawngreen;
  /* background-color: yellow; */
  display: flex;
  justify-content: space-around;
  flex-direction: column;
  align-items: center;
  flex-wrap: nowrap;
  background: rgba(0, 0, 0, 0.4);
  text-shadow: 0 0 5px black;
}

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

.key kbd {
  display: block;
  font-size: 2.4rem;
  font-weight: bold;
}

.sound {
  font-size: 1rem;
  font-family: "Franklin Gothic Medium", "Arial Narrow", Arial, sans-serif;
  text-transform: uppercase;
  letter-spacing: 1px;
}