CSS动画实现边框变厚效果

<div class="box"></div>

.box {
  width: 100px;
  height: 100px;
  margin: 50px auto;
  border: solid #007acc;
  border-width: 2px;
  animation: borderThicken 2s ease-in-out infinite alternate;
}

@keyframes borderThicken {
  from {
    border-width: 2px;
  }
  to {
    border-width: 10px;
  }
}

@keyframes borderBottomGrow {
  0% {
    border-bottom-width: 1px;
  }
  100% {
    border-bottom-width: 8px;
  }
}

.box {
  width: 120px;
  height: 120px;
  border: none;
  border-bottom: solid #ff5722;
  animation: borderBottomGrow 1.5s infinite alternate;
}

@keyframes pulseBorder {
  0% {
    border-width: 4px;
    border-color: #3f51b5;
    transform: scale(1);
  }
  100% {
    border-width: 12px;
    border-color: #ff4081;
    transform: scale(1.05);
  }
}

.box {
  width: 80px;
  height: 80px;
  border: solid;
  border-width: 4px;
  border-color: #3f51b5;
  animation: pulseBorder 1.8s ease-out infinite alternate;
}