"it shrinks when any part of the unit shrinks, because of the mechanical linkages, the pulling tension transmit throughout the unit. since he had 4 points of shrinkage, helps spreads out the tension instead of a single point of failure. its really well designed. as for the concern where snow gets into the bends, entire bottom can be one solid surface like covered with a fabric so there's no space for dirt to accumulate in the hinges. but from a mechanical strength standpoint, the many moving parts does weaken the structure overall significantly and stepping on uneven surfaces would quickly damage the mechanism. a better design would be passively bending material, like how the bottom of our feet conforms to the surface rather than bending like a door hinge."