.counter

@property --milliseconds {
  inherits: false;
  initial-value: 0;
  syntax: '<integer>';
}

body {
  min-height: 100vh;
  display: grid;
  place-items: center;
  background: hsl(10, 10%, 10%);
}

.counter {
  position: relative;
  counter-reset: ms var(--milliseconds);
  animation: count 1s steps(100) infinite;
}

.counter:after {
  content: counter(ms);
  position: absolute;
  top: 0;
  left: 0;
  font-size: 5rem;
  transform: translate(-50%, 0);
  color: hsl(0, 0%, 100%);
  font-weight: bold;
  font-family: sans-serif;
}

@keyframes count {
  to {
    --milliseconds: 100;
  }
}