[up to this 3D shape]
- Start from
- Close the bridge on one side (east) and rotate 90 degrees counterclockwise
in order to obtain a 3x2 rectangle with a
stack of three tiles in the North-West position with the top one (third floor)
of type backslash and connected to the Central-West tile
- Open by hinging the stack about the South side (first-second floor) and
the West side (second-third floor) into the final shape
