style.css

*, *::after, *::before {
  box-sizing: border-box;
}

html {
  background: #000000;
  width: 100%;
  min-height: 100%;
  display: grid;
  align-content: center;
  justify-content: center;
  overflow: hidden;
}

.stack {
  list-style: none;
  padding: 0;
  display: grid;
  align-content: center;
  grid-template-rows: 1fr;
  grid-template-columns: 1fr;
}

.digit {
  color: #ffffff;
  font-family: 'Open Sans', sans-serif;
  font-size: 70vh;
  grid-row: 1;
  grid-column: 1;
  opacity: .1;
}

.stack .digit:nth-child(0) {
  animation: cycle 3.3s 0s infinite;
}

.stack .digit:nth-child(1) {
  animation: cycle 4s 0.4s infinite;
}

.stack .digit:nth-child(2) {
  animation: cycle 4s 0.8s infinite;
}

.stack .digit:nth-child(3) {
  animation: cycle 4s 1.2s infinite;
}

.stack .digit:nth-child(4) {
  animation: cycle 4s 1.6s infinite;
}

.stack .digit:nth-child(5) {
  animation: cycle 4s 2s infinite;
}

.stack .digit:nth-child(6) {
  animation: cycle 4s 2.4s infinite;
}

.stack .digit:nth-child(7) {
  animation: cycle 4s 2.8s infinite;
}

.stack .digit:nth-child(8) {
  animation: cycle 4s 3.2s infinite;
}

.stack .digit:nth-child(9) {
  animation: cycle 4s 3.6s infinite;
}

.stack .digit:nth-child(10) {
  animation: cycle 4s 4s infinite;
}

@keyframes cycle {
  0%, 25% {
    opacity: 1;
  }
  25%, 100% {
    opacity: 0.1;
  }
}