@keyframes lights {
  0% {
    background-position: top;
  }
  100% {
    background-position: bottom;
  }
}

#lights {
  height: 69px;
  background: url(./img/BdGY6tH.png);
  background-size: auto 138px; /* total height = frame height * number of frames */
  animation: lights 1s infinite steps(2, jump-none);
}