Prompt reply for Weekend Prompt 15: Top Down or Bottom Up?
Top Down or Bottom Up
In Worldbuilding, this is a question you'll often see when you have been in the hobby/community for a while. For those new to the question, it's asking us 'How do we build our worlds?' - usually, folks will have a style they prefer that typically falls into one of these two categories.
Top Down refers to a Macro to Micro approach - where we build from something Big down to something Small. Often with this approach, you'd define the world itself or an entire continent before you began worldbuilding other things like cities, cultures, characters, etc. In rare cases where you're dealing with an entire galaxy, you might create some broad strokes to set some galactic rules before you dive into specific planets, then specific continents, etc... all the way down to a specific character, event, or even object. With this approach, we define a lot of the large rules early on for how things work in our setting. If there are gods, we know that. If there are space-aliens, we know that. If there is somewhere in our setting that is super dangerous... we know that. And, those things we know can help guide us as we go deeper and deeper and get smaller and smaller. How the character dresses when we get to that point will be defined by their culture, which is in some ways defined by their geography, which is defined by how the world works.
Bottom Up is the reverse of this. You start with a small idea like a single character, and you begin building things up around them. I like to think of the Bottom Up approach like the White Room from The Matrix.
With a Bottom Up approach, we build the world around a single point. It could be something like a character, a building, or a specific event. Every time we need something new, we create it from where we are. If we start a scene in a specific room and we have no established worldbuilding... whatever is outside that door becomes part of the setting the second we write about it. Often, this approach will achieve the exact same end as a Top Down approach.
What do I do?
Well... that answer is simple! I do both!
Which method I use depends a lot on what I'm doing. My freewrites for example are rarely ever given proper worldbuilding, but if they were to be looked at from a worldbuilding standpoint they'd definitely be Bottom Up... because I start with a character, concept, or event and then I build just enough world around that focal point to pull off the story I'm trying to tell.
Another example of Bottom Up that I've used is something I've discussed before in my Building the City of Modnae worldbuilding post. While a lot of Trothguard is Top Down, this city didn't exist at all until I was jokingly suggested to build a transit system while waiting in the hospital for the birth of my daughter.

The entire city was built from the concept of a transit system. Of course, with a random transit system, I need a city for it to exist in, and I need to know how it runs, what prompted its creation, and who lives in the city. After that, I built events within the city, and defined some external problems that ties this city to the rest of the country. Bottom Up definitely worked very well in this case, and as we see from the fact that I jammed it into my main setting afterwards... this method can be combined with Top Down settings very easily!
In the case of my world as a whole, Trothguard was created in a Top Down fashion because it is designed to be primarily a Tabletop Roleplaying setting that is more-or-less system agnostic. I could run Ironsworn or Errant in Trothguard just as easily as I could run any edition of D&D, or Pathfinder.
For the Trothguard setting, I started with the cosmos: I wanted to define how many worlds were in the system that this planet shares, how many moons it had, and what role gods played in this setting. I chose how deities were formed, what magic was like here, what level of technology the world had. I then dove into what continents the world contains, and of those, I chose to focus on a single one which conveniently is the name of my project and the name of the continent.
With a map of the continent, I started to think about what continent-wide issues existed that weren't tied to countries/kingdoms. After that, I defined what kingdoms exist, who rules them and how they rule, and vaguely paired them with real-life cultures to define what their architecture and clothing were like... and I just kept going down from there until I built out the actual starting setting that players began in: The Greater Rondid Area.

I left blank spaces here on purpose so that we could flesh it out as we went - though we never ended up playing through much of this campaign so it never had further areas added.
Final Thoughts
So, as you can see - there's no real right or wrong way to build a setting. Top Down, Bottom Up, or some mix of the two that we could technically call Middle Out... it's all valid! Whatever works for you for what you're doing is what you should use! I still advise not over-building, and to focus on the stuff you need and to fill in the rest with kind of placeholder text/broad strokes that you can later refine. Most of the countries on my map for example are about as shallow as possible. I made rulers and lightly dashed some culture together, but until I have reason to set a story there or create a campaign for folks to play in... those areas don't get actual worldbuilding treatment. It's enough to know that they exist and to have some understanding of how they fit in the world. More will come naturally as you need. It's easy to get lost in the weeds if you try to worldbuild every detail, and that can halt your actual project. It's hard to make a quest for a group of players when you spend 4 hours diving down the rabbit hole of how ancient Roman salt mines work.
cough Not that I know anyone who did that. Nope, no sir. Not me. cough
Until next time, happy Worldbuilding folks... and a big thanks to for the super fun prompt. I do love a good meta-analysis of worldbuilding as a hobby!