3D transform issue in firefox - css

Question

I have a JSFiddle showing a flipping card, It works in chrome as I would expect but the depth perspective in firefox is flat and I'm not sure where the issue is.
I have tried adding:
transform-style: preserve-3d;
and
perspective: 1000;
to all classes (like card) I could with no luck.
The HTML structure is:
<div id="card-container">
<button id="card-flip">Flip the card</button>
<div id="card">
<div class="front card-surface"><!-- front -->
<p>The front</p>
</div>
<div class="back card-surface"><!-- back -->
<p>The back</p>
</div>
</div>
</div>
The simplified CSS is:
#card-container{
position: relative;
background-color:#888;
width: 300px;
height: 450px;
margin:0 auto;
}
#card-flip{
display:none;
}
#card{
margin:10px auto;
width: 100%;
height: 400px;
}
.card-surface{
margin-top:5px;
width: 280px;
height: 180px;
padding:10px;
}
.front{
background-color:#7B78E8;
}
.back{
background-color:#78AFE8;
}
/* Only apply 3d effects if they exist in the browser */
#card-container.threed{
height: 250px;
perspective: 1000;
}
.threed #card-flip{
background-color:transparent;
position:relative;
top:220px;
width:100%;
height:40px;
background-color:#99E5FF;
}
.threed #card-flip:focus{
outline:0;
}
.threed #card-flip:hover{
background-color:#49A5BF;
}
#card-flip:hover + #card .card-surface{
box-shadow: 0 0px 50px rgba(0,0,0,0.9);
transition: all .8s ease-in-out;
}
.threed #card{
height:200px;
}
.threed #card .front {
float: none;
position: absolute;
top: 0;
left: 0;
z-index: 900;
transform: rotateX(0deg) rotateY(0deg);
transform-style: preserve-3d;
backface-visibility: hidden;
}
.threed #card.flip .front {
z-index: 900;
border-color: #eee;
background: #333;
box-shadow: 0 15px 50px rgba(0,0,0,0.2);
transform: rotateY(180deg);
}
.threed #card .back {
float: none;
position: absolute;
top: 0;
left: 0;
z-index: 800;
border: 1px solid #ccc;
text-shadow: 1px 1px 1px rgba(0,0,0,0.6);
transform: rotateY(-180deg);
transform-style: preserve-3d;
backface-visibility: hidden;
}
.threed #card.flip .back {
z-index: 1000;
background-color:#ccc;
transform: rotateX(0deg) rotateY(0deg);
}
.threed #card .card-surface{
background-color:$base-white;
transition: all .8s ease-in-out;
width: 280px;
height: 180px;
padding:10px;
}
I have seen working examples like This one. Can anyone tell me what I am missing or is it not possible with this structure?

Answer 1

I have figured out the issue.
Here is a new version of the fiddle.
The problem was that I did not have the px after the perspective property. this was ignored by chrome but not firefox. I also applied The perspective to the wrong element in the demo so even though I had tried to ad the px before it didn't work.