Physics boundaries

Hello,

I have a game that spawns balloons upward. The balloons come through an entryway and after they are all spawned, the entryway closes. However, when balloons are ready to be spawned again, the entryway opens and more balloons come up. The problem is, when a user tilts their device, the balloons already on the screen, push down on the balloons being spawned. What I am trying to do is: prevent the balloons that are already on the screen from entering the spawning area when balloons are being spawned. How would I do this? I think I need a boundary that allows newly spawned balloons to pass through it, but not balloons that have already been spawned. Is there any way I could do this?

Any help would be appreciated.
Thanks. [import]uid: 47722 topic_id: 13206 reply_id: 313206[/import]

you probably need to filter your collisions
i think there was a sample code on this site for such things [import]uid: 16142 topic_id: 13206 reply_id: 48466[/import]