#anniu{
  overflow:hidden;
}
.anniu1{
     position:relative;
  margin:0 auto;
  width:200px;
  }
  .anniu1 a{
  width: 200px;
    height: 50px;
    position: relative;
    text-transform: uppercase;
    color: #333;
    font-weight: 700;
    letter-spacing: 1px;
        font-family: Arial;
    border: none;
    font-size: 15px;
    outline: none;
    display: block;
    line-height: 50px;
    position: relative;
  text-align:center;
    z-index: 1;
  border: 1px solid #333;
  }
#anniu>a{
  transition:color .5s ease; 
}

#anniu .anniu_border{
  z-index:0;
  background:var(--color);
  width:30px;
  height:30px;
  transform:rotate(45deg);
}

#anniu>.anniu_border:nth-of-type(1){
  top:-65px;
  left:-60px; 
  position: absolute;
      transition: 0.5s;
}

#anniu>.anniu_border:nth-of-type(2){
  top:-65px;
  right:-60px;
  position: absolute;
      transition: 0.5s;
}

#anniu>.anniu_border:nth-of-type(3){
  bottom:-65px;
  left:-60px;
  position: absolute;
      transition: 0.5s;
}

#anniu>.anniu_border:nth-of-type(4){
  bottom:-65px;
  right:-60px;
  position: absolute;
      transition: 0.5s;
}

#anniu:hover .anniu_border{
  width:160px;
  height:160px;
}

#anniu:hover a{
  color:#FFF;
  transition:color 2s ease;
    z-index:2;
}