We knew a few things immediately: You could not modify exterior walls and windows, but you can modify interior walls and objects. We knew we were going to create large shells in which we placed lots that we could then build. Why shells? Well, in order to create true high rises, or even six-floor apartments, we needed to craft specific models. Otherwise, they wouldn’t look like apartments, and trying to create sufficient assets for Build Mode would have been very difficult for an expansion. By using these shells, we get something that looks like an apartment, fleshes out the city, but still gives us a platform on which to build.