Top pieces are loose while bottom pieces are fixed.
Exterior support is inserted into adjacent buildings, while the top pieces fall over when unsupported.
There are aftershocks from the earthquake periodically, retracting the internal support.
Several buildings begin with a visible internal support, helping to indicate that the building components can be stacked.
The support doesn’t penetrate the top-most piece, which must be held by hand or connected by a bridge, if available, lest it fall over.
The support moving rapidly upward and retreating after the puzzle is finished causes all the pieces to fall off and scatter, providing an automatic reset.
