@keyframes changewidth {
  from {
    background-color: #c146ff;
  }

  to {
    background-color: #8adb49;
  }
}

body {
  animation-duration: 1s;
  animation-name: changewidth;
  animation-timing-function: ease-in-out;
  animation-iteration-count: infinite;
  animation-direction: alternate;
}