* {
  font-family: Arial, sans-serif, monospace;
  font-size: 8vh;
  text-shadow: 0 0 3vh;
  text-align: center;
}
body {
  background: url('piece_of_mind___iron_maiden___wallpaper_by_lloydgrasm3_denolzu-fullview.jpg') no-repeat center fixed;
  background-size: cover;
  width: device-width;
}
button {
  background: linear-gradient(60deg, rgb(100, 0, 214), rgb(0, 0, 0));
  border: 0.5vw solid black;
  width: 10vw;
  height: 10vw;
  margin: 0 15%;
  color: black;
  border-radius: 100%;
 
}
.disabled-button {
  background: gray;
  border: 0.5vw solid black;
  color: black;
}
.active-button {
  transition: opacity 0.3s;
}
.active-button:hover {
  opacity: 0.9;
  cursor: pointer;
}
.active-button:active {
  opacity: 0.8;
}
@media (orientation: portrait) {
  button {
    width: 20vw;
    height: 20vw;
    margin: 0;
  }
}