.rainbow-title {
  display: block;
  /* stays centered normally */
  text-align: center;
  /* centers the text inside */
  font-size: xx-large;
  font-weight: bold;

  background: linear-gradient(
    90deg,
    red,
    #ff7f00,
    yellow,
    green,
    royalblue,
    indigo,
    violet,
    red
  );
  background-size: 400% 100%;
  background-repeat: no-repeat;

  background-clip: text;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;

  animation: rainbow-move 6s linear infinite;
}

@keyframes rainbow-move {
  0% {
    background-position: 0% 0;
  }

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