Css 圆形按钮边框长度动画

body {
  margin: 0;
  padding: 0;
  height: 100vh;
  width: 100vw;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: rgba(0, 0, 0, 0.9);
}

.button {
  position: relative;
  width: 500px;
  height: 100px;
  background-color: #083a65;
  border: none;
  color: white;
  font-size: 18px;
  border-radius: 10px;
  overflow: hidden;
}

.button .text {
  position: absolute;
  width: calc(100% - 4px);
  height: calc(100% - 4px);
  top: 2px;
  left: 2px;
  background-color: #083a65;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 9px;
}

.button .top {
  position: absolute;
  left: 5px;
  top: 0px;
  width: 100%;
  height: 2px;
  background-color: yellow;
  animation: animate-top 1500ms linear;
}

.button .top::after {
  content: "";
  position: absolute;
  top: 0;
  right: 5px;
  width: 10px;
  height: 10px;
  background-color: yellow;
}

.button .right {
  position: absolute;
  right: 0;
  top: -5px;
  width: 2px;
  height: 100%;
  background-color: yellow;
  animation: animate-right 1500ms linear;
}

.button .right::before {
  content: "";
  position: absolute;
  bottom: -5px;
  right: 0;
  width: 10px;
  height: 10px;
  background-color: yellow;
}

.button .bottom {
  position: absolute;
  right: 0;
  bottom: 0px;
  width: 100%;
  height: 2px;
  background-color: yellow;
  animation: animate-bottom 1500ms linear;
}

.button .bottom::before {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 10px;
  height: 10px;
  background-color: yellow;
}

.button .left {
  position: absolute;
  left: 0;
  bottom: 0;
  width: 2px;
  height: 100%;
  background-color: yellow;
  animation: animate-left 1500ms linear;
}

.button .left::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 10px;
  height: 10px;
  background-color: yellow;
}

@keyframes animate-top {
  0% {
    width: 0px;
  }
  25% {
    width: 100%;
  }
  50% {
    width: 100%;
  }
  75% {
    width: 100%;
  }
  100% {
    width: 100%;
  }
}

@keyframes animate-right {
  0% {
    height: 0;
  }
  25% {
    height: 0;
  }
  50% {
    height: 100%;
  }
  75% {
    height: 100%;
  }
  100% {
    height: 100%;
  }
}

@keyframes animate-bottom {
  0% {
    width: 0;
  }
  25% {
    width: 0;
  }
  50% {
    width: 0;
  }
  75% {
    width: 100%;
  }
  100% {
    width: 100%;
  }
}

@keyframes animate-left {
  0% {
    height: 0;
  }
  25% {
    height: 0;
  }
  50% {
    height: 0;
  }
  75% {
    height: 0;
  }
  100% {
    height: 100%;
  }
}

 <button class="button">
   <span class="top"></span>
   <span class="right"></span>
   <span class="bottom"></span>
   <span class="left"></span>
   <span class="text">Animated button</span>
 </button>