大致思路：首先给 three-d-box 设置一个 transition是不可少的
然后每个 a 标签里面有两个 span 一个叫 font 一个叫 back，默认状态下 font 旋转0度，也就是没旋转，back 旋转-90度，现在只能看得到 font 看不到 back 当鼠标移动到上面去的时候（任务5这两个样式控制，移动到上面来的时候旋转90度），控制 three-d-box旋转90度，这样，原来的 font 就旋转到后面去了，back 就变成正面朝前了 就可以看到了。
效果如图：
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>制作3D旋转导航</title>
<style>
@import url("http://www.w3cplus.com/demo/css3/base.css");
/*任务一：引入本地字体文件*/
@font-face {
font-family: 'sansationregular';
src: url('http://www.w3cplus.com/demo/css3/3DAnimationDropdownMenu/sansation_regular-webfont.eot');
src: url('http://www.w3cplus.com/demo/css3/3DAnimationDropdownMenu/sansation_regular-webfont.eot?#iefix') format('http://www.w3cplus.com/demo/css3/3DAnimationDropdownMenu/embedded-opentype'),
url('http://www.w3cplus.com/demo/css3/3DAnimationDropdownMenu/sansation_regular-webfont.woff') format('woff'),
url('http://www.w3cplus.com/demo/css3/3DAnimationDropdownMenu/sansation_regular-webfont.ttf') format('truetype'),
url('http://www.w3cplus.com/demo/css3/3DAnimationDropdownMenu/sansation_regular-webfont.svg#sansationregular') format('svg');
font-weight: normal;
font-style: normal;
}
body {
background-color:#edecec;
}
/* basic menu styles */
.nav-menu {
display: block;
background: #74adaa;
width:950px;
margin: 50px auto 150px;
}
.nav-menu > li {
display: inline;
float:left;
border-right:1px solid #94c0be;
}
.nav-menu > li:last-child {
border-right: none;
}
.nav-menu li a {
color: #fff;
display: block;
text-decoration: none;
/*调用本地字体*/
font-family: 'sansationregular';
-webkit-font-smoothing: antialiased;
-moz-font-smoothing: antialiased;
font-smoothing: antialiased;
text-transform: capitalize;
overflow: visible;
line-height: 20px;
font-size: 20px;
padding: 15px 30px 15px 31px;
}
/* animation domination */
.three-d {
/* 任务三、设置3D舞台布景 */
-webkit-perspective: 200px;
-moz-perspective: 200px;
-ms-perspective: 200px;
-o-perspective: 200px;
perspective: 200px;
/*任务四、设置3D舞台布景过渡效果*/
-webkit-transition: all .07s linear;
-moz-transition: all .07s linear;
-ms-transition: all .07s linear;
-o-transition: all .07s linear;
transition: all .07s linear;
position: relative;
}
.three-d:not(.active):hover {
cursor: pointer;
}
/*任务五、给不是当前状态的3D舞台的悬浮与聚焦状态设置变形效果*/
.three-d:not(.active):hover .three-d-box,
.three-d:not(.active):focus .three-d-box {
-wekbit-transform: translateZ(-25px) rotateX(90deg);
-moz-transform: translateZ(-25px) rotateX(90deg);
-o-transform: translateZ(-25px) rotateX(90deg);
-ms-transform: translateZ(-25px) rotateX(90deg);
transform: translateZ(-25px) rotateX(90deg);
}
.three-d-box {
/*任务六、给3D舞台中“.three-d-box”设置过渡与变形效果*/
-webkit-transition: all .3s ease-out;
-moz-transition: all .3s ease-out;
-ms-transition: all .3s ease-out;
-o-transition: all .3s ease-out;
transition: all .3s ease-out;
-webkit-transform: translatez(-25px);
-moz-transform: translatez(-25px);
-ms-transform: translatez(-25px);
-o-transform: translatez(-25px);
transform: translatez(-25px);
-webkit-transform-style: preserve-3d;
-moz-transform-style: preserve-3d;
-ms-transform-style: preserve-3d;
-o-transform-style: preserve-3d;
transform-style: preserve-3d;
-webkit-pointer-events: none;
-moz-pointer-events: none;
-ms-pointer-events: none;
-o-pointer-events: none;
pointer-events: none;
position: absolute;
top: 0;
left: 0;
display: block;
width: 100%;
height: 100%;
}
/*任务七、给导航设置3D前，与3D后变形效果*/
.front {
-webkit-transform: rotatex(0deg) translatez(25px);
-moz-transform: rotatex(0deg) translatez(25px);
-ms-transform: rotatex(0deg) translatez(25px);
-o-transform: rotatex(0deg) translatez(25px);
transform: rotatex(0deg) translatez(25px);
}
.back {
-webkit-transform: rotatex(-90deg) translatez(25px);
-moz-transform: rotatex(-90deg) translatez(25px);
-ms-transform: rotatex(-90deg) translatez(25px);
-o-transform: rotatex(-90deg) translatez(25px);
transform: rotatex(-90deg) translatez(25px);
color: #FFE7C4;
}
.front, .back {
display: block;
width: 100%;
height: 100%;
position: absolute;
top: 0;
left: 0;
background: #74adaa;
padding: 15px 30px 15px 31px;
color: white;
-webkit-pointer-events: none;
-moz-pointer-events: none;
-ms-pointer-events: none;
-o-pointer-events: none;
pointer-events: none;
-webkit-box-sizing: border-box;
box-sizing: border-box;
}
/*任务八、设置导航当前状态与悬浮状态下的背景效果*/
.nav-menu li .active .front,
.nav-menu li .active .back,
.nav-menu li a:hover .front,
.nav-menu li a:hover .back {
background-color: #51938f;
-webkit-background-size: 5px 5px;
background-size: 5px 5px;
background-position: 0 0, 30px 30px;
background-image: -webit-linear-gradient(45deg, #478480 25%, transparent 25%, transparent 75%, #478480 75%, #478480), linear-gradient(45deg, #478480 25%, transparent 25%, transparent 75%, #478480 75%, #478480);
background-image: -moz-linear-gradient(45deg, #478480 25%, transparent 25%, transparent 75%, #478480 75%, #478480), linear-gradient(45deg, #478480 25%, transparent 25%, transparent 75%, #478480 75%, #478480);
background-image: -ms-linear-gradient(45deg, #478480 25%, transparent 25%, transparent 75%, #478480 75%, #478480), linear-gradient(45deg, #478480 25%, transparent 25%, transparent 75%, #478480 75%, #478480);
background-image: -o-linear-gradient(45deg, #478480 25%, transparent 25%, transparent 75%, #478480 75%, #478480), linear-gradient(45deg, #478480 25%, transparent 25%, transparent 75%, #478480 75%, #478480);
background-image: linear-gradient(45deg, #478480 25%, transparent 25%, transparent 75%, #478480 75%, #478480), linear-gradient(45deg, #478480 25%, transparent 25%, transparent 75%, #478480 75%, #478480);
}
.nav-menu ul {
position: absolute;
text-align: left;
line-height: 40px;
font-size: 14px;
width: 200px;
-webkit-transition: all 0.3s ease-in;
-moz-transition: all 0.3s ease-in;
-ms-transition: all 0.3s ease-in;
-o-transition: all 0.3s ease-in;
transition: all 0.3s ease-in;
-webkit-transform-origin: 0px 0px;
-moz-transform-origin: 0px 0px;
-ms-transform-origin: 0px 0px;
-o-transform-origin: 0px 0px;
transform-origin: 0px 0px;
-webkit-transform: rotateX(-90deg);
-moz-transform: rotateX(-90deg);
-ms-transform: rotateX(-90deg);
-o-transform: rotateX(-90deg);
transform: rotateX(-90deg);
-webkit-backface-visibility: hidden;
-moz-backface-visibility: hidden;
-ms-backface-visibility: hidden;
-o-backface-visibility: hidden;
backface-visibility: hidden;
}
/*任务九、显示下拉导航菜单，并其设置一个变形效果*/
.nav-menu > li:hover ul {
display: block;
-webkit-transform: rotateX(0deg);
-moz-transform: rotateX(0deg);
-ms-transform: rotateX(0deg);
-o-transform: rotateX(0deg);
transform: rotateX(0deg);
}
</style>
</head>
<body>
<div id="nav">
<ul class="nav-menu clearfix unstyled">
<li><a href="#" class="three-d active">
Home
<span class="three-d-box"><span class="front">Home</span><span class="back">Home</span></span>
</a></li>
<li><a href="#" class="three-d">
Services
<span class="three-d-box"><span class="front">Services</span><span class="back">Services</span></span>
</a></li>
<li><a href="#" class="three-d">
Products
<span class="three-d-box"><span class="front">Products</span><span class="back">Products</span></span>
</a></li>
<li><a href="#" class="three-d">
About
<span class="three-d-box"><span class="front">About</span><span class="back">About</span></span>
</a></li>
<li><a href="#" class="three-d">
Contact
<span class="three-d-box"><span class="front">Contact</span><span class="back">Contact</span></span>
</a></li>
<li><a href="#" class="three-d">
Blog
<span class="three-d-box"><span class="front">Blog</span><span class="back">Blog</span></span>
</a>
<ul class="clearfix unstyled drop-menu">
<li><a href="#" class="three-d">
Html5
<span class="three-d-box"><span class="front">Html5</span><span class="back">Html5</span></span>
</a></li>
<li><a href="#" class="three-d">
Css3
<span class="three-d-box"><span class="front">Css3</span><span class="back">Css3</span></span>
</a></li>
<li><a href="#" class="three-d">
JavaScript
<span class="three-d-box"><span class="front">JavaScript</span><span class="back">JavaScript</span></span>
</a></li>
<li><a href="#" class="three-d">
Videogames
<span class="three-d-box"><span class="front">Videogames</span><span class="back">Videogames</span></span>
</a></li>
</ul>
</li>
<li><a href="#" class="three-d">
Shop On-line
<span class="three-d-box"><span class="front">Shop On-line</span><span class="back">Shop On-line</span></span>
</a></li>
</ul>
</div>
</body>
</html>