Some feedback:
You can place a bunch of pillars in the location of the same pillar, you'll see it change colors a bit, but the Resources costs won't go up. But when you remove the pillars that are in the same location, their cost
is removed from the resources costs, even though all except the first one was not added to that. So you can get into negative resource costs.
When trying to build a 2x1 building with stairs in alternating location (as opposed to making 1 big high staircase with a side-door on each floor), I can't build stars on the first raised level. This is the design ID (it also shows the negative resources used):
oY6XwJCCNMFkkevPQkw4gtjDlwFUtJRSHYQdHsQvewQzKmpAHV FXoYAKvgEYZwRH
The visible ceiling between the floor is where I would like to place the stairs.
Also, I find it pretty difficult to get a view closer to the building, looking down from above. I can get closer, but then it will just view the bottom... I can't manage look inside the top of a tower for example.
I managed to put a wall on a wall by placing a ceiling on the first walls, adding the next walls, then removing the ceiling you never wanted. But that's just a silly workaround :).
Edit:
I noticed that too. In case his picture was not clear enough yet, the game lets you all walls/doorways/windows between pillars that are in the middle of foundations but the tool doesn't.
Which can be used to make his example of a 2x2 building on a 3x3 foundation, which would be like this:
http://i.imgur.com/qD6JKkn.png
Edited:
This is a very user-friendly way of building! It would be pretty cool if this was further developed. Adding the other building materials and a list of used materials mostly. You even already have the functionality of building walls between pillars that are in the middle of a foundation, unlike the other designer tools I've seen, nice! :)