Corona Tip: Physics
Note to Corona physics users! Collisions between physical objects in different Corona display groups will not function properly if you move ONE of the groups but not ALL of the groups. Why is this? The physics engine requires a common "coordinate space" to internally calculate collisions. If this space is disrupted by moving one of the groups, the collisions will behave (mathematically) as if the objects were using the original position of their display group. In order to circumvent this, you must move objects on a "per-object basis" within a group, versus moving the group as a whole.