A shoe may comprise an upper and a comfort sole attached to an outsole, the comfort sole having a radius of curvature at any point of a line from a heel to a toe and interfacing with outsole, wherein the lowest point of comfort sole and outsole, called the center of mass or balance point of the sole or natural balance point of the shoe, when placed on a substantially horizontal reference plane defines a transition zone of the roll of the foot having the highest radius of the comfort sole and the outsole, and in that the center of mass is behind point (B) of the metatarsals; and a rigid shell interposed between the upper and the comfort sole.