One major example of evolution in games is the Pokemon series; in these games evolution indicates a change from one type of Pokemon to a more advanced form. An evolved Pokemon will usually have enhanced abilities and be able to learn new moves and attacks. However, once a Pokemon has evolved it cannot change back to its previous stage. Pokemon typically only have 2 or 3 stages of evolution, although rare Pokemon usually cannot evolve at all. Pokemon Evolution is usually spontaneous, but the player can press the B button to prevent the Pokemon from completing its evolution. When a Pokemon is about to evolve, it glows with a bright white light, and when the light has faded, the Pokemon will have changed shape.
Pokemon usually evolve once they have gained a certain amount of experience
. Pokemon gain experience from successful battles, or alternatively from being left at the Day-Care center. Alternatively, some Pokemon can only evolve when they are exposed to a Specific type of Evolution Stone. For example, Pikachu
can only evolve if it is exposed to a Thunder Stone
The only other way to evolve a Pokemon is through a trade with another trainer. This is very rare and only happens with a couple of cases - for example Haunter will only evolve into Gengar after being traded with another player.