Collision detection

I'm making a game with a ball that will bounce off a shape with varying-angled faces on its way to the 'target'...

I know how to use Polygon definition to apply to my shape, but it suggests no more than 8 points, and my shape is far more complex than that.

So, is there a more elegant way of defining my shape? I mean, is there a way for the application to know automatically how my ball should bounce off my shape, without having to define my shape with a separate Polygon?

And if not, is there a performance hit by using, say, 21 points on a single shape, compared to 7 points on 3 separate shapes?

Take a look at this: http://www.scirra.com/forum/polygon-whats-better_topic48484.html

Answers my question exactly, thank you 7Soul.

(how do I keep missing these threads?!)