When the OPTIMUS PRIME truck cab is changed into a robot, the truck trailer opens up into a MINI-CON base station all by itself!   Create Super OPTIMUS PRIME - Change the robot into a torso form and the base station raises up automatically to become the legs of the awesome robot!  Combine the torso and legs and you've created Super OPTIMUS PRIME! When the OPTIMUS PRIME robot is changed back into the truck cab, the base station closes up to form the truck trailer all by itself!  The MINI-CON base station has ramps, firing stations, runways and storage areas for MINI-CON figures.  Also features electronic lights and sounds.