效果例图：
1、首先呈现的是html代码：
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="./3.css">
<title>Document</title>
</head>
<body>
<nav class="navbar">
<ul class="nav-list">
<li class="nav-item">
<a href="#" class="nav-link">home</a></li>
<li class="nav-item">
<a href="#" class="nav-link">about</a>
<ul class="dropdown">
<li class="dropdown-item"><a href="#" class="dropdown-link">Our Team</a></li>
<li class="dropdown-item"><a href="#" class="dropdown-link">Our Story</a></li>
<li class="dropdown-item"><a href="#" class="dropdown-link">Careers</a></li>
</ul>
</li>
<li class="nav-item">
<a href="#" class="nav-link">Services</a>
<ul class="dropdown">
<li class="dropdown-item"><a href="#" class="dropdown-link">web</a></li>
<li class="dropdown-item"><a href="#" class="dropdown-link">html</a></li>
<li class="dropdown-item"><a href="#" class="dropdown-link">dockewr</a></li>
<li class="dropdown-item"><a href="#" class="dropdown-link">nginx</a></li>
<li class="dropdown-item"><a href="#" class="dropdown-link">hahah</a></li>
</ul>
</li>
<li class="nav-item">
<a href="#" class="nav-link">Contact</a>
</li>
</ul>
</nav>
</body>
</html>2、其次最关键的css3样式代码：
body{
margin: 0;
font-family: Arial, Helvetica, sans-serif;
background-color: #f0f0f0;
display: flex;
justify-content: center;
align-items: center;
min-height: 100vh;
}
.navbar{
background-color: #333;
width: 100%;
position: fixed;
top: 0;
left: 0;
}
.nav-list{
list-style: none;
margin: 0;
padding: 0;
display: flex;
justify-content: center;
}
.nav-item{
position: relative;
}
.nav-link{
display: block;
padding: 15px 20px;
color: white;
text-decoration: none;
font-size: 18px;
transition: background-color 0.3s,transform 0.3s;
position: relative;
z-index: 1;
}
.nav-link:hover{
background-color: #008c8c;
transform: scale(1.1);
}
.nav-link::after{
content: "";
position: absolute;
left: 50%;
width: 0;
height: 3px;
background-color: #f8f400;
transition: all 0.4s;
bottom: 0;
z-index: 1;
}
.nav-link:hover::after{
left: 0;
width: 100%;
}
.dropdown{
display: none;
/* height: 0px; */
position: absolute;
top: calc(100% + 2px);
left: -5px;
background-color: #444;
list-style: none;
margin: 0;
padding: 0;
overflow: hidden;
border-radius: 3px;
min-width: 150px;
z-index: 1000;
opacity: 0;
transform: translateY(-10px);
transition: background-color 0.6s ease-in-out;
}
.dropdown-item{
position: relative;
}
.dropdown-link{
display: block;
padding: 15px 20px;
color: white;
text-decoration: none;
font-size: 18px;
transition: background-color 0.3s;
}
.dropdown-link::after{
content: "";
position: absolute;
bottom: 0;
left: 50%;
width: 0px;
height: 2px;
transition: all 0.4s ease-in-out;
}
.dropdown-link:hover{
background-color: #008c8c;
}
.dropdown-link:hover::after{
left: 0;
width: 100%;
background-color: #f8f400;
}
.nav-item:hover .dropdown{
display: block;
/* height: 300px; */
opacity: 1;
transform: translateY(0);
}总结：CSS太强大了，只是我们现在的学习知识不够，不能够很好的驾驭它，
