Pokémon involves the catching and training of fictional creatures called "Pokémon" and using them to battle other Trainers. Each successive generation of games builds upon this concept by introducing new Pokémon, items, and gameplay concepts. Some of the general concepts were featured elsewhere in the franchise before being introduced to the games; double battles appeared in the anime long before appearing in the games and are similar to the Pokémon Powers introduced in the Pokémon Trading Card Game, which also introduced , the phenomenon of Pokémon being different colors than the original. Pokémon competitive play is where players around the world battle each other with Pokémon. However, it requires some strategy involving having Pokémon with high stats and picking supereffective moves.