li{list-style: none;}
a{text-decoration: none;}
.nav{
  width:100%;
  height:40px;
  /* float:left; */
  text-align: center;
  border-top:1px solid #566473; 
  padding-top:20px; 
  display: block;
}
.nav ul{font-size:0;}
.nav ul li{float:left;margin-top: 5px;}
.nav ul li a{
  font-size:14px;
  color:#566473;
  line-height:40px;
  padding:10px 15px;
  margin:0 10px;
  position:relative;
}
.nav ul li a::before,.nav ul li a::after{
  content:'';
  display:block;
  width:25%;
  height:30%;
  position:absolute;
  border:2px solid #566473;
  border-radius:3px;
  transition: all 0.6s ease;
}
.nav ul li a::before{
  top:0;
  left:0;
  border-right-color:transparent;
  border-bottom-color:transparent;
}
.nav ul li a::after{
  bottom:0;
  right:0;
  border-left-color:transparent;
  border-top-color:transparent;
}
.nav ul li a:hover::before,.nav ul li a:hover::after{
  width:100%;
  height:100%;
}
ol{
  margin:10px; 
}
.arc-list{
  margin-top: 5px;
}
.arc-list-item{
  margin-top: 10px;
}