围绕圆圈的径向css3动画

<div class="circle"></div>

.circle {
  width: 100px;
  height: 100px;
  border-radius: 50%;
  background-color: blue;
  animation: radial-animation 3s infinite;
}

@keyframes radial-animation {
  0% {
    border-radius: 50%;
  }
  50% {
    border-radius: 50% / 0%;
  }
  100% {
    border-radius: 50%;
  }
}