What CSS is supported in the Style property?

So I’m working on finishing up my floorplan which is made with a picture elements card.

There I need a few buttons, to do some stuff like turn off all the lights, the top one is a state-label which I’m able to style quite nice, I however cannot get the text to center, normally I would use text-align: center, but that dosen’t work in Home Assistant.

The last two are service buttons, these I can’t even change the font color no matter how much I try, normally I would use Color: white, no again, no luck.

In the documentation is says you can style with CSS and then a link to the CSS wikipedia page, but that dosen’t seem to be the case.

Is there some kind of documentation of what CSS is supported and what isn’t?

Udklip1

I also can’t get “box-shadow” to work on an image in the same picture elements card.

Few code snippets:
https://pastebin.com/KknGU9M2
https://pastebin.com/EFiBQRHK