In some species, medusae are only produced when the water temperature exceeds a certain level.

Hydrogen burning occurs in a shell surrounding an inert helium core until the steadily increasing core temperature exceeds.

They can not, however, be used where the ambient temperature exceeds the capability of the built-in circuitry.

When the temperature exceeds safe limits the bar becomes full; the player will be immobilized for several seconds while the bike cools down.