Sooo I do have opinions here although I'm not a big writer so please do correct me if I'm giving bad advice
However the approach I'd take with a project like this is to start with the core-idea of your world, what is the one thing that it all hinges around? After that you logically connect each element into the core idea and you see if it fits, if it does not you cut it.
For example: Core idea: A world where everyone is a floating sphere!Logical connections: How do spheres manipulate the world? Do they have fold out arms? Do they have telekinetic powers? If they don't have arms then they cant have an arm-wrestling club, but maybe they can have a physic dojo - or maybe they have a sport of bumping into each other or rolling in races?
What do sphere people eat? Do they have mouths? Obvs a sphere who only eats grass would be very different from one that only eats cows. A grass eating sphere might have evolved tiny pores on its body to ingest the grass and it would mow grass like a big shaver!
How do spheres age? Do they turn into cubes? Are the cities of sphere people built out of the cube bodies of past lifeless spheres that have been reused as bricks?? This implies a lot! For example it gives us ideas about how the spheres grieve and what their beauty standards might be ~ do they find more-spehereish-spheres beautiful, do they value the wisdom of a lumpy less round sphere?
So basically you take your core-idea and you extrapolate it; you've already got a bunch of ideas and plans in mind, so you can use those as a guide, but I'd also say don't let your existing ideas hold you back!
EDIT: Also is this page supposed to be really hard to read??

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