It is not easy to push this toy out of its equilibrium. Each swing out of the state of equilibrium causes the toy to come back to its starting balance point.

The stability of the equilibrium is caused by uneven mass distribution inside the toy. The base of the toy is round and the centre of mass is located near the base. Sometimes the whole base is just a half-round iron weight.

The head of the toy has to be comparatively light, compared with the rest of the toy body, so that Always Up could swing back by itself from each position.

Two kinds of force affect the swaying doll: the ground reaction force and the doll's weight located in the centre of gravity. Since both forces are not aligned they interact and as a result of this interaction the unbalanced moment of force makes the doll regain its balance.

The above phenomenon is illustrated by the picture. 'Always-down', is the doll which falls down since its centre of gravity is located high.

'Always-up' remains in the state of permanent balance: it always regains balance as a little ball inside a bigger hemisphere, in contrast to transitory balance in 'Always-down', like a little ball at the top of a bigger hemisphere.

In this way the leaning doll attains the minimal amount of potential gravitation energy; the lower the centre of gravity the lower the potential gravitation energy.