Product "Out Of Stock" Extra class

[saniaja]

Hello,
Can't find solution for my problem. I'm trying to add a custom class to the product card. When the product is out of stock I need the product card to have "opacity 0.5" (or be half transparent).

Is there a way to do so with the simple line of code? I assume it has something to do with the following coding...
{if $product.quantity > 0}{else} ... {/if}

Sample of what I'm trying to reach in the image attached..

Would appreciate community help.

Thanks.

[SliderFlash]