Allows to create groups layers which collisions are isolated from each other.
Looks like Box2D (the underlying physics system) supports layering, but it needs a lot of investigation, specially how does C2 relates your object to Box2D
Guess it is not a simple task to hack the standard Physics behavior then. Only if. Other Physics behaviors have the option for layering collisions but they don't work the same way as the std behavior for me. Maybe if Ashley can give some direction on this.