* Transformation: Bakugan are small, spherical objects that transform into larger, more powerful creatures when they roll across a special "Baku-Core" card.
* Baku-Cores: Baku-Cores are cards with specific attributes and powers that trigger the Bakugan's transformation.
* Rolling Action: When a Bakugan rolls across a Baku-Core, its energy activates, causing it to pop open and morph into its creature form.
* Different Transformation Styles: There are different types of Bakugan, each with their own unique transformation and battle styles.
It's important to remember that the Bakugan themselves don't have any physical opening mechanism like a hinge or a lid. The "opening" is a visual effect created through the transformation process.