Why is blue circle not spinning in the center of itself [duplicate]

Answer 1

You need transform-box: fill-box;

circle {
  animation: grow 2s infinite;
  transform-origin: center;
  transform-box: fill-box;
}
@keyframes grow {
  0% {
    transform: scale(1);
  }
  50% {
    transform: scale(0.5);
  }
  100% {
    transform: scale(1);
  }
}