SCP Foundation

Hi. Since I got interested by the scp foundation I've become a frequent visitor here and I quickly learned that the site's appearance is different for different articles. Like, the forum here is what I'd call a "classic look", but there are some newer scps and the site looks much fresher despite the same url (at first glance I even thought it was a different site).

I'm learning the wiki's html and text editing capabilities but I haven't even once come across a post talking about this, that's why I'm asking the following question:

how?

Is this an automatic feature for the newer articles?

If you still don't know what I'm reffering to, it's this:
https://i.imgur.com/u8Gm4W9.png - "classic"
https://i.imgur.com/dtKTo0D.png - "newer"

The "newer" looking sites appear in the Cannon Hub or some SCP pages that want to look modern. (or in other words not using the Sigma-9 component) while some keep the "classic" look others change the theme with their own components to make the site look "newer" or "diffrent" while keeping the URL. Hope I helped!

The 'classic' the standard site appearance - Any deviation is extra CSS theme being applied on top.

Coincidentally, the 'newer' one is a theme I made, with no official relation, technically speaking.