Two double storey apartments occupy three floors, one placed on top of the other such that access to both apartment units are on the courtyard level, with one unit connected to another floor below the courtyard level, and the other joins to another floor above the courtyard level.
This is the view of those 2 apartments from the side.
Stacking two pairs of these interlocking apartments on top of each other produces a three storey high courtyard.
But stacking these apartments on top of each other such that the courtyards flip from one side to the opposite produces a six storey high courtyard.
The courtyards flip from one position to the other to create the 6-storey courtyards.