body {
  margin: 0;
}

main {
  height: 95vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

.circle {
  width: 50px;
  height: 50px;
  background-color: white;
  border: 5px solid tomato;
  border-radius: 50%;

  animation: resize 2s ease-in-out infinite;
}

@keyframes resize {
  from {
    opacity: 1;
  }
  to {
    height: 400px;
    width: 400px;
    opacity: 0;
  }
}