<div class="container">
  <span>10</span>
  <span>9</span>
  <span>8</span>
  <span>7</span>
  <span>6</span>
  <span>5</span>
  <span>4</span>
  <span>3</span>
  <span>2</span>
  <span>1</span>
  <span>0</span>
</div>

html,
body {
  height: 100%;
  width: 100%;
  font-family: monospace;
  background-color: black;
  overflow: hidden;
}

.container {
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  position: fixed;
  filter: contrast(20);
  background-color: black;
  overflow: hidden;
}

span {
  color: rgb(230,255,230);
  font-size: 8rem;
  font-weight: 700;
  text-align: center;
  text-transform: uppercase;
  line-height: 1;
  filter: blur(0.2rem);
  display: block;
  transition: all 1.5s ease;
  opacity: 0;
  filter: blur(0.6rem);
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  &:nth-child(1) {
    animation: letteranim 11s infinite ease;
    animation-delay: 0s;
  }
  &:nth-child(2) {
    animation: letteranim 11s infinite ease;
    animation-delay: 1s;
  }
  &:nth-child(3) {
    animation: letteranim 11s infinite ease;
    animation-delay: 2s;
  }
  &:nth-child(4) {
    animation: letteranim 11s infinite ease;
    animation-delay: 3s;
  }
  &:nth-child(5) {
    animation: letteranim 11s infinite ease;
    animation-delay: 4s;
  }
  &:nth-child(6) {
    animation: letteranim 11s infinite ease;
    animation-delay: 5s;
  }
  &:nth-child(7) {
    animation: letteranim 11s infinite ease;
    animation-delay: 6s;
  }
  &:nth-child(8) {
    animation: letteranim 11s infinite ease;
    animation-delay: 7s;
  }
  &:nth-child(9) {
    animation: letteranim 11s infinite ease;
    animation-delay: 8s;
  }
  &:nth-child(10) {
    animation: letteranim 11s infinite ease;
    animation-delay: 9s;
  }
  &:nth-child(11) {
    animation: letteranim 11s infinite ease;
    animation-delay: 10s;
  }
}

@keyframes letteranim {
  0% {
    opacity: 0;
    filter: blur(0.6rem);
  }
  5% {
    opacity: 1;
    filter: blur(0.2rem);
  }
  10% {
    opacity: 1;
    filter: blur(0.2rem);
  }
  20% {
    opacity: 0;
    filter: blur(0.6rem);
  }
  100% {
    opacity: 0;
    filter: blur(0.6rem);
  }
}