h1
{ color: blue;
}

body 
{ background-image: url("GetNeuroFuelX.JPEG");
  background-size: cover;
  background-repeat: no-repeat;
  background-position: center center;
  background-attachment: fixed; 
}

 @media only screen and (max-width: 768px)
{ body
  { background-image: url("mobile.png");
   background-size: 100vw 100vh;
   background-position: center center;
   background-size: cover;
  }
}