How to make a "No Unit" and "Fly Only" zone?

Editor Discussion
1

I was inspired by seeing the Daelaam Ark in the “Enemy Within” (HoTS Mission) and got the brilliant idea to make a ladder-match worthy map on a Protoss Ship, but I realized the map started falling apart early on due to the fact that Reapers and Colossi exist… So I am wondering how to make a cliff wall that units cannot climb over nor fly (No Units Allowed) and how to make areas that only Flying Units can go through (because I’m a noob and don’t know how) to represent ships in the empty space. If you need clarification, I can try to make a visual form.

Thank you all for the assistance!

EDIT: I found out reducing ALL cliff levels to 0 prevents ground, and you can build invisible doodads. Thank you all!

2

Can you create an area and make it a “no ground units” area? (properties of the area)
Else there should be special terrain that is flat but where units can’t walk on.