<div></div>

@import url("https://fonts.googleapis.com/css2?family=Exo:wght@600&display=swap");

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  width: 100vw;
  min-height: 100vh;
  font-family: "Exo", Arial, sans-serif;
  background-color: #222;
  color: #fff;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 1.5rem;
  gap: 10px;
}

div::after {
  font-weight: 900;
  font-size: 50vh;
  background-image: linear-gradient(#ff5722, #9c27b0);
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

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

div {
  counter-reset: num var(--num);
  animation: counter 50s infinite alternate ease-in-out;
}

div::after {
  content: counter(num);
}

@keyframes counter {
  from {
    --num: 0;
  }
  to {
    --num: 100;
  }
}