Evolving Bakugan in the game, use a certain card called a Reference Card. It states the requirements for that Bakugan to be able to evolve or swap out, with another certain Bakugan. They often require a Power Level as Splight and Quake Dragonoid need a Power Level of 2 each. Most Bakugan Reference Cards, have a prerequisite for the Bakugan evolving. For example, the Quake Dragonoid Evolution Card requires that the Bakugan must be a Dragonoid under 650 Gs. Some Bakugan Reference Cards require the Bakugan, to be in a certain Attribute. The Reference Cards are purple.