How does those pull back toy cars work?

Anyone know how those pull back toy cars work? Those cars that you pull back and when u release it it goes. Ihave one and i cant open it to see how it works.








And there are also some that starts moving slow after you pull back and release and soon enough, it moves faster. Anyone knows how those work too?





Thanks.|||When this toy car is pulled back a few inches, it travels right across


the room. The energy must be stored quickly but released slowly. This


is achieved using two different gear trains in the same tiny gearbox -


when pulled back, the spring tightens fifteen times faster than when


it unwinds. The innovation lies in two floating gears - the axes of


gears 2 and 4 move along two slots in the gearcage depending on the


tangential forces acting on them. Explore the details of this


ingenuous mechanism.