PhysicsBodyCollisionLayer Property

The physics layers this area is in.

Collidable objects can exist in any of 32 different layers. These layers work like a tagging system, and are not visual. A collidable can use these layers to select with which objects it can collide, using the CollisionMask property.

A contact is detected if object A is in any of the layers that object B scans, or object B is in any layer scanned by object A. See Collision layers and masks in the documentation for more information.