body {
  background-image: url("todd.png");
  background-size: 5%;
  min-height: 100vh;
}

@keyframes change {
  0% {
    background: no-repeat linear-gradient(#a104ee, #000000);
  }
  100% {
    background: no-repeat linear-gradient(#000000, #a104ee);
  }
}

html {
  background: no-repeat linear-gradient(#000000, #a104ee);
  animation: change linear 1s infinite;
}