Query about how to achieve a certain effect

[gloopy]

Hi,

I saw this today:

http://s0.2mdn.net/1062493/Wellingto...ions728x90.swf

And really like way the yellow animated stars are replaced by blue animated stars, with a central number of the opposite colour to the background being present in the centre.

I wondered if anyone might be able to throw any light on how those effects are done please?

Is it using masks, or AS, or both?

Any advice much appreciated.

Thanks

[marshdabeachy]

Just masks, you can create that without any Actionscript.