Once upon a time Space-frogs on Zelin lived in small houses in the swamps, and rarely interacted with each other. But after the invention of one respected frog professor, everything has changed. Now the whole planet is one big friendly city. It is home to frogs of different sizes and colors:
- poisonous frogs-doctors - these are large earth frogs and tiny bright frogs. Thanks to the poison that their skin produces and the ancient knowledge of herbal medicine, they are the best doctors;
- tree frogs - builders, thanks to their suckers on their paws, climb well into trees, where they collect materials (dry trees and twigs) that are used for construction and further clear the forest;
- space-frogs scientists - work and live in a secluded town of Scientists, where incredible inventions are born. This town is covered with a protective energy dome.
The constant attacks of the Space-beavers from the Trade Guild complicate frog life. Traders often try to steal new technologies created by frog scientists. Spase-beavers also cut down and export special iron trees left only on Zelin. These trees are an important part of the planet's ecological chain, but the Space-beavers do not care about it. Wood is very valuable and used by them to build their spacecraft. In addition, each stick that remains is sold very expensively. The only defenders of the forest are the special squad of frog rescuers, which hides the iron trees. They hide the iron trees covering them by light-absorbing pellicle and making them invisible.