title: Clip-path doesn't work in Firefox and IE
body: <p>I have a <code>nav</code> element that on mouse hover reveal my menu, it works fine on Safari and Chrome however not in Firefox nor in IE:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>/* start nav menu morph */
  
  nav {
    width: 23%;
    background: #222222;
    color: rgba(255, 255, 255, 0.87);
    -webkit-clip-path: circle(16px at 30px 24px);
    clip-path: circle(16px at 30px 24px);
    -webkit-transition: -webkit-clip-path 0.5625s, clip-path 0.375s;
    transition: -webkit-clip-path 0.5625s, clip-path 0.375s;
  }
  nav:hover {
    -webkit-transition-timing-function: ease-out;
    transition-timing-function: ease-out;
    -webkit-transition-duration: 0.75s;
    transition-duration: 0.75s;
    -webkit-clip-path: circle(500px at 225px 24px);
    clip-path: circle(500px at 225px 24px);
  }
  nav a {
    width: 100%;
    display: block;
    line-height: 50px;
    padding: 0 20px;
    color: inherit;
    cursor: pointer;
    -webkit-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
  }
  nav a:hover {
    background: #ffe082;
  }
  nav a:active {
    background: #ffca28;
  }
  .nav-sim {
    position: absolute;
    right: 0;
    top: -6px;
  }
  .navicon {
    padding: 23px 20px;
    cursor: pointer;
    -webkit-transform-origin: 32px 24px;
    -ms-transform-origin: 32px 24px;
    transform-origin: 32px 24px;
  }
  .navicon div {
    position: relative;
    width: 20px;
    height: 2px;
    background: rgb(254, 70, 70);
  }
  .navicon div:before,
  .navicon div:after {
    display: block;
    content: "";
    width: 20px;
    height: 2px;
    background: rgb(254, 70, 70);
    position: absolute;
  }
  .navicon div:before {
    top: -7px;
  }
  .navicon div:after {
    top: 7px;
  }
  .fa-sim {
    font-size: large;
    margin-left: 5px;
  }
  /* end nav menu morph */</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;noscript&gt;
    &lt;style&gt;
      #navmenusim {
        display: none;
      }
    &lt;/style&gt;
  &lt;/noscript&gt;
  &lt;nav class="nav-sim" id="navmenusim"&gt;
    &lt;div class="navicon"&gt;
      &lt;div&gt;&lt;/div&gt;
    &lt;/div&gt;
    &lt;a href="#" class="" rel=""&gt;Home&lt;i class="fa fa-home icon i-sim fa-sim"&gt;&lt;/i&gt;&lt;/a&gt;
    &lt;a href="#" class="" rel=""&gt;Blog&lt;i class="fa fa-rss icon i-sim fa-sim"&gt;&lt;/i&gt;&lt;/a&gt; 
    &lt;a href="#" class="" rel=""&gt;Contact&lt;i class="fa fa-mail icon i-sim fa-sim"&gt;&lt;/i&gt;&lt;/a&gt; 
  &lt;/nav&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>The menu in Firefox and IE is always visible, the clip-path doesn't work. How to fix it?</p>