body {
  background: linear-gradient(-45deg, #da0000, #0008ffe5, #23d5a2d8, #2f2fbce5);
  background-size: 400% 400%;
  -webkit-animation: gradient 15s ease infinite;
  animation: gradient 15s ease infinite;
}

@-webkit-keyframes gradient {
  0% {
    background-position: 0% 50%;
  }

  50% {
    background-position: 100% 50%;
  }

  100% {
    background-position: 0% 50%;
  }
}

@keyframes gradient {
  0% {
    background-position: 0% 50%;
  }

  50% {
    background-position: 100% 50%;
  }

  100% {
    background-position: 0% 50%;
  }
}