the object of the present invention is a device by means of which simulation of the lengthening of shortening of , for example , a limb is obtaining by construction of a telescoping structure , the mutual sliding of which , and therefore the lengthening or shortening is controlled by means of threads that are rolled or unrolled from a disk shaped like one or more side - by - side pulleys . thanks also to the action of a counteracting spring . the movement of the spools is controlled by a circuit that registers shaking and therefore playing with the toy according to the equation , more playing = more growth .