Just to clarify a point in this thread: when working with physics bodies and collisions, the objects can be in different display groups. However, you can not move/position the groups independently of each other. For example, you can’t put some physical objects in “myGroup1”, put other physical objects in “myGroup2”, then set “myGroup2.y = 100” (thus moving the entire group). This will break collision detection, because while the display objects in that group will move, the associated physics bodies will not.
Best regards,
Brent