css实现按钮边框流动特效

.my_btn {
  width: 100px;
  height: 50px;
  text-align: center;
  margin-top: 10px;
  line-height: 50px;
  background-color: #fff;
  position: relative;
  overflow: hidden;
  border-radius: 25px;
  z-index: 9;
}
@keyframes mymove {
  from {
    transform: rotateZ(0);
    transform-origin: left top;
  }
  to {
    transform: rotateZ(360deg);
    transform-origin: left top;
  }
}

.my_btn::after {
  content: "";
  border-radius: 25px;
  width: calc(100% - 2px);
  height: calc(100% - 2px);
  background-color: #fff;
  position: absolute;
  top: 1px;
  left: 1px;
  z-index: -1;
}

.my_btn::before {
  content: "";
  width: 100%;
  height: 100%;
  background-color: #f00;
  position: absolute;
  top: 50%;
  left: 50%;
  z-index: -2;
  animation: mymove 3s infinite linear;
}

　利用元素的before  after伪元素  利用动画加定位层级实现，具体代码如上