[up to this 3D shape]
- Start from
- Close both flaps against opposite sides (east and west) of the "tube"
- Move lower tile of the West wall towards the lonely tile of the south wall
and change their hinging side
- Simultaneously push apart the two lower tiles of the East wall (also changing
their hinging side, hence hinging about their upper side, some stretching involved)
- Finally open the flap to obtain the final shape.
