*{margin:0;padding:0;box-sizing:border-box;font-size:0;}
nav a{
  
  color:inherit;
  font-size:14px;
}
nav li{
  display:inline-block;
  width:150px;
  height:30px;
  padding:10px 20px;
  background-color:#000;
  border:1px solid #000;
  text-align:center;
  color:#fff;
  position:relative;
}
nav li:hover{
  background-color:#fff;
  color:#000;
}
nav li>ul{
  display:none;
}
nav li:hover>ul{
  display:flex;
  position:absolute;
  top:30px;
  left:0px;
}