Bounding circle

Hi,

Is it possible to make a bounding circle instead of a bounding box?

The objects should bounce INSIDE the circle.
I have now a bounding box outside the circle, but the objects exceeds the circle at the corners.

I was thinking of making an array of Points on the edge of a circle and when the object is < or > then do something… but that would be a lots of if/else statements.

Any of you knows a better solution to achive this?

Thanks!