If you need some more help with it, let me know and I’ll see if I can help :)
Sorry to double post, but I thought you might also be interested in this:
You’ve declared z-index on a couple of other elements, so maybe have a look at the layering of your elements. I’ve declared z-index of 0 on the container element ‘card’, which might resolve that.
I think it also might have to do with not explicitly declaring the height and width. Unfortunately, I think you might have to give them some values, rather than just having them be auto, as I’ve don in my CodePen.
Finally, I don’t think this will have any impact, but you’ve linked your stylesheets etc in the header tag within the body tag. You should probably link these in the head tag which is outside/above of the body tag.
Hope it all helps, but in any case have a merry Christmas :)