I got this in THE bundle but it is so relaxing, simple yet brilliant and enthralling, that I purchased it again!
As a small suggestion I support what was already mentioned in the previous comments: more in-depth graphical settings.
I also have something else but might be not-doable/sci-fi: would it be possible to have the shapes interact physically with each other only when the user interacts with them first? It could prevent the stuttering for big towers even when the building is freshly built (and perhaps "premature collapsing" also).
Thanks :)