Path app copycat v2

Fixed cross-browser compatibility.

HTML

<h1>"Add" menu from the Path application in pure CSS.</h1>
<p>by Denys Mishunov (<a href="http://goo.gl/wRIKL" title="Original blog post">http://goo.gl/wRIKL</a>)</p>


<nav>
    <!-- We don't really care about specific value of the input, but Opera doesn't trigger the state for this checkbox without it. -->
    <input type="checkbox" id="shownav" value="true" class="visuallyhidden" />
    <label for="shownav" class="ir">Show navigation</label>        
    <ul class="menu">
        <li><a href="#">1</a></li>
        <li><a href="#">2</a></li>
        <li><a href="#">3</a></li>
        <li><a href="#">4</a></li>
        <li><a href="#">5</a></li>
    </ul>
</nav>

CSS

/* Basics */
body {
    font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
    padding: .5em;
}
h1 {
    font-weight: bold;
    font-size: 1.2em;
}
p {
    margin-bottom: 1.5em;
}
nav {
    background: #efede9;
    border: 1px solid #bfbeba;
    position: relative;
    width: 14em;
    height: 14em;
}        
/* Some helper classes from the HTML5 Boilerplate  */
/*        .visuallyhidden { border: 0; clip: rect(0 0 0 0); height: 1px; margin: -1px; overflow: hidden; padding: 0; position: absolute; width: 1px; }*/
.ir { display: block; border: 0; text-indent: -999em; overflow: hidden; background-color: transparent; background-repeat: no-repeat; text-align: left; direction: ltr; *line-height: 0; }

/* The toggle */
label[for="shownav"], .menu, input#shownav {
    position: absolute;
    bottom: 5%;
    left: 5%;
    padding: 0;
    margin: 0;             
} 
input#shownav,
input#shownav:checked {
    -webkit-appearance: none;
    -moz-appearance: none;
    border: none;
    background: transparent;
    outline: none;
    height: 2.4em;
    width: 2.4em;
    padding: 0;
    margin: 0;
    z-index: 2;
}
label[for="shownav"], .menu a {
    /* Basis for the circles */
    -webkit-border-radius: 50%;
    -moz-border-radius: 50%;
    border-radius: 50%;

    -moz-background-clip: padding;
    -webkit-background-clip: padding-box;
    background-clip: padding-box;

    -webkit-box-shadow: 0 0 0 3px #fff, 0 0 0 4px #949390, 0px .1em .15em 4px #bdbbb7;
    -moz-box-shadow: 0 0 0 3px #fff, 0 0 0 4px #949390, 0px .1em .15em 4px #bdbbb7;
    box-shadow: 0 0 0 3px #fff, 0 0 0 4px #949390, 0px .1em .15em 4px #bdbbb7;

}       
label[for="shownav"] {
    display: block;
    color: #fff;
    z-index: 3; /* to initially overlap the navigation items */
    height: 1em;
    width: 1em;
    line-height: 1;
    font-size: 2.4em;
    cursor: pointer; 
    pointer-events: none;     
                
    background-color: #e76040;
    background-image: -webkit-gradient(radial,...