How to create a responsive navigation bar with dropdown in CSS?

Following is the code to create a responsive navigation bar with dropdown −

Example

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1" />
<style>
*,*::after,*::before{
   box-sizing: border-box;
}
.menu-btn {
   font-size: 18px;
   font-weight: bold;
   display: inline-block;
   text-align: center;
   background-color: #040008;
   color: white;
   padding: 20px;
   font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
   border: none;
   width: 100%;
}
.dropdown-menu {
   position: relative;
   display: inline-block;
}
.menu-content {
   display: none;
   position: absolute;
   width: 100%;
   background-color: #017575;
   min-width: 160px;
   z-index: 1;
}
nav{
   background-color: #017575;
   width: 100%;
}
.links,.links-hidden{
   display: inline-block;
   color: rgb(255, 255, 255);
   text-decoration: none;
   font-size: 18px;
   font-weight: bold;
   padding: 20px;
}
.links-hidden:hover,.links:hover {
   background-color: rgb(8, 107, 46);
}
.dropdown-menu:hover .menu-content {
   display: block;
}
.dropdown-menu:hover .menu-btn {
   background-color: #3e8e41;
}
.hamburger {
   color: white;
   font-weight: bolder;
   display: none;
}
@media screen and (max-width: 880px) {
      nav a:not(:first-child) {
      display: none;
   }
   nav a.hamburger {
      float: right;
      display: block;
      padding: 12px;
   }
   .dropdown-menu{
      display: none;
   }
   nav.openNav a.hamburger {
      position: relative;
   }
   nav.openNav a {
      float: none;
      display: block;
      text-align: center;
   }
}
nav.openNav div.dropdown-menu{
   display: block;
   width: 100%;
}
</style>
</head>
<body>
<nav>
<a class="links" href="#">HOME</a>
<a class="links" href="#">EMPLOYEES</a>
<a class="links" href="#">CAREER</a>
<a class="links" href="#">Our History</a>
<a class="links" href="#">Fund Us</a>
<a class="links" href="#">More Info</a>
<div class="dropdown-menu">
<button class="menu-btn">Open <</button>
<div class="menu-content">
<a class="links-hidden" href="#">Contact Us</a>
<a class="links-hidden" href="#">Visit Us</a>
<a class="links-hidden" href="#">About Us</a>
</div>
</div>
<a class="hamburger">☰</a>
</nav>
<script>
var x = document.getElementsByTagName("nav")[0];
function toggleNav() {
   if (x.className === "") {
      x.className = " openNav";
   } else {
      x.className = "";
   }
}
document.querySelector(".hamburger").addEventListener("click", toggleNav);
</script>
</body>
</html>