body { 
    padding: 2ch;
    background: linear-gradient(124deg, #ff2400, #e81d1d, #e8b71d, #e3e81d, #1de840, #1ddde8, #2b1de8, #dd00f3, #dd00f3);
    background-size: 1800% 1800%;
    -webkit-animation: rainbow 10s ease infinite;
    -z-animation: rainbow 10s ease infinite;
    -o-animation: rainbow 10s ease infinite;
    animation: rainbow 10s ease infinite;
  }
  
  @-webkit-keyframes rainbow {
      0%{background-position:0% 82%}
      50%{background-position:100% 19%}
      100%{background-position:0% 82%}
  }
  
  @-moz-keyframes rainbow {
      0%{background-position:0% 82%}
      50%{background-position:100% 19%}
      100%{background-position:0% 82%}
  }
  
  @-o-keyframes rainbow {
      0%{background-position:0% 82%}
      50%{background-position:100% 19%}
      100%{background-position:0% 82%}
  }
  
  @keyframes rainbow { 
      0%{background-position:0% 82%}
      50%{background-position:100% 19%}
      100%{background-position:0% 82%}
  }