body {
  background: #000;
  -webkit-user-select: none;
     -moz-user-select: none;
      -ms-user-select: none;
          user-select: none;
  cursor: default;
}

.rainbow {
  width: 400px;
  height: 100px;
  -webkit-transform: translate(-100px, 0);
          transform: translate(-100px, 0);
  background: -webkit-linear-gradient(left, red, orange, yellow, green, blue, indigo, violet, red, orange, yellow, green, blue, indigo, violet, red);
  background: linear-gradient(left, red, orange, yellow, green, blue, indigo, violet, red, orange, yellow, green, blue, indigo, violet, red);
  display: inline-block;
  position: absolute;
  margin: auto;
  top: 0;
  left: 0;
  right: 0;
  -webkit-animation: rainbow 1s linear infinite;
          animation: rainbow 1s linear infinite;
}

.text {
  width: 600px;
  height: 100px;
  background: #fff;
  mix-blend-mode: screen;
  text-align: center;
  line-height: 100px;
  position: absolute;
  font-size: 40px;
  margin: auto;
  font-weight: bold;
  top: 0;
  left: 0;
  right: 0;
}

@-webkit-keyframes rainbow {
  100% {
    -webkit-transform: translate(100px, 0);
            transform: translate(100px, 0);
  }
}

@keyframes rainbow {
  100% {
    -webkit-transform: translate(100px, 0);
            transform: translate(100px, 0);
  }
}