Have an “extra” room, what do I even do with it?

I know this might be out of the scope since it's not exactly a stylistic choice, but I also wasn't sure where else it might go and home decorating seemed like the relevant descriptor.

I recently got a new apartment that's not only significantly larger than any previous one I've ever had, but it comes with (sort of) three rooms. One room I've claimed for my computer area and added the general living room vibe to (sofa, tv, general 'guest' space with the computer chair doubling as an extra seating spot if needed), and another room is quite obviously the bedroom, but that leaves the third room that I have absolutely no idea what to do with.

It hosts the cat's litterbox, which is absolutely non-negotiable because she needs a lot of space and I don't want that right next to my computer or sofa. But that also makes it not exactly an ideal dining room because not only do I not really need a dining room (I'd personally rather eat at my desk, or at the table in front of the sofa), but also, eating within 3 feet of a litterbox is not an appealing concept.

I also don't want to separate the living room and computer area because it's too big to just be a computer space, and I'm really liking the communal feel of having the combined space when I have guests over, particularly friends who also game and can set up in the same area. I already still have extra space in that room anyway, so it's not like I'm hurting for space there either to justify separating them.

Outside a dining room though, I genuinely have no idea what I could possibly do with the space. I'm not exactly an interior decorating pro and have only ever had tiny apartments before, so now I don't even know what to do with this much space. (And I live alone currently so it's not like I have to allot space for my partner's things any time soon.)

Any suggestions or ideas? If it helps any, it does get a LOT of natural light.

Rough approximation of apartment layout here. (This isn't to scale, it's a rough layout, but it's got the general feel down.)