A motor assembly with coaxial shafts is provided which can be produced at low costs and in which a plurality of motors can be disposed with their respective rotary shafts arranged coaxially to one another with high coupling and assembling accuracy in a simple structure. One game device is disclosed for use with a plurality of game pieces and includes a three-dimensional pathway segmented into a plurality of distinct spaces in which the game pieces fit. Application to the preparation of structures and composite materials which can be heated by the Joule effect or which can be used for electromagnetic shielding.