This may actually be a better question for Muun, she's more thorough about worldbuilding than I am and I often take her lead on it. Anything amazingly cool about worldbuilding is all her, I'm more her assistant in this regard. She often comes up with a premise for the world and I go "oh that's very cool' and basically work on making that work.

The worldbuilding I help supply has more to do with character functionality (the geo-economical reality the characters live in, how they traveled if they traveled, etc), and researching the cultural influence I'm pulling from to make the world building real.