CodePen Embed - 3D navigation with pure CSS

<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>

@import url("https://www.w3cplus.com/demo/css3/base.css");

@font-face {
    font-family: 'sansationregular';
    src: url('https://www.w3cplus.com/demo/css3/3DAnimationDropdownMenu/sansation_regular-webfont.eot');
    src: url('https://www.w3cplus.com/demo/css3/3DAnimationDropdownMenu/sansation_regular-webfont.eot?#iefix') format('https://www.w3cplus.com/demo/css3/3DAnimationDropdownMenu/embedded-opentype'),
         url('https://www.w3cplus.com/demo/css3/3DAnimationDropdownMenu/sansation_regular-webfont.woff') format('woff'),
         url('https://www.w3cplus.com/demo/css3/3DAnimationDropdownMenu/sansation_regular-webfont.ttf') format('truetype'),
         url('https://www.w3cplus.com/demo/css3/3DAnimationDropdownMenu/sansation_regular-webfont.svg#sansationregular') format('svg');
    font-weight: normal;
    font-style: normal;
}
body {
  background-color:#edecec;
}
ul, li {
  list-style: none outside none;
}
/* basic menu styles */
.nav-menu {
  display: block;
  background: #74adaa;
  width:951px;
  margin: 50px auto 150px;
}
.nav-menu > li {
  display: inline;
  float:left;     
  border-right:1px solid #94c0be;
  position: relative;
}
.nav-menu > li:last-child {
  border-right: none;
}
.nav-menu li a {
  color: #fff;
  display: block;
  text-decoration: none;
  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 {
  -webkit-perspective: 200px;
  -moz-perspective: 200px;
  -ms-perspective: 200px;
  -o-perspective: 200px;
  perspective: 200px;
  -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;
}

.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 {
  -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%;
}

.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;
}
.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;
  left: -40px;
  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;
}
.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);
}

This Pen is owned by 大漠 on CodePen.

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External CSS

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External JavaScript

//cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js