.bb, .bb::before, .bb::after {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
}
.bb {
  width: 450px;
  height: 450px;
  margin: auto;
  color: #69ca62;
  box-shadow: inset 0 0 0 1px rgba(105, 202, 98, 0.5);
}
.bb::before, .bb::after {
  content: '';
  z-index: -1;
  margin: 25%;
  box-shadow: inset 0 0 0 2px;
  animation: clipMe 8s linear infinite;
}
.bb::before {
  animation-delay: -4s;
}
.bb:hover::after, .bb:hover::before {
  background-color: rgba(255, 0, 0, 0.3);
}
@keyframes clipMe {
  0%, 100% {
    clip: rect(0px, 225px, 2px, 0px);
  }
  25% {
    clip: rect(0px, 2px, 225px, 0px);
  }
  50% {
    clip: rect(223px, 225px, 225px, 0px);
  }
  75% {
    clip: rect(0px, 225px, 225px, 223px);
  }
}
*, *::before, *::after {
  box-sizing: border-box;
}