assign a cacheAsBitmapMatrix for ball:
also, create a background using a bitmap or enable the background's cacheAsBitmap
I will test with bitmapMatrix.
But is it necessarily to add a background bitmap, if I am using stage color instead?
it's not necessary but you can increase performance by doing that even if it means creating a stage colored movieclip or bitmap.
Weird, but I just tested with Matrix and ir acts the same or even slower. At least I had a hope for a minute
So I'm still seeking for the answer to this problem.