body {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 100vh;
  font-family: Arial;
  background: #262626;
  margin: 0;
  padding: 0;
  --main-color: #484848;
}

li {
  list-style: none;
  color: var(--main-color);
  display: inline;
  font-size: 5em;
  letter-spacing: 15px;
  animation: pre-load 3s linear infinite;
}

@keyframes pre-load {
  0% {
    color: var(--main-color);
    text-shadow: none;
  }

  20% {
    color: var(--main-color);
    text-shadow: none;
  }

  40% {
    color: #fff900;
    text-shadow: 0 0 7px #fff900, 0 0 50px #ff6c00;
  }

  60% {
    color: var(--main-color);
    text-shadow: none;
  }

  80% {
    color: var(--main-color);
    text-shadow: none;
  }

  100% {
    color: var(--main-color);
    text-shadow: none;
  }
}

li:nth-child(1) {
  animation-delay: 0.2s;
}

li:nth-child(2) {
  animation-delay: 0.4s;
}

li:nth-child(3) {
  animation-delay: 0.6s;
}

ul li:nth-child(4) {
  animation-delay: 0.8s;
}

ul li:nth-child(5) {
  animation-delay: 1s;
}

ul li:nth-child(6) {
  animation-delay: 1.2s;
}

ul li:nth-child(7) {
  animation-delay: 1.4s;
}

ul li:nth-child(8) {
  animation-delay: 1.6s;
}

ul li:nth-child(9) {
  animation-delay: 1.8s;
}

ul li:nth-child(10) {
  animation-delay: 2s;
}