Inverting transparency

HI, I'm sure that there must be an easy answer to this but can anyone please explain how to invert transparency? I would like to create an effect where the central area of the circle or shape is transparent and the outer edge opaque. Any help might just stop me from going mad!
Thanks in advance
Zap

The following method will work on all transparencies, but you mentioned circle, so we'll do that one.

Create shape. Add transparency (circular). Double click on the transparency line somewhere in the middle.
Click the centre node and move the slider to 100% transparency.
Click the end node and move the slider to 0% transparency.
Click the centre node and play with the slider to get the effect you want.

The centre node can be dragged along the line to change the effect and multiple extra nodes can be added by double clicking on the transparency line.

Attachment 130136

Thanks Chris,

It works a treat!

And you can do the same with a Fill, making the inner node(s) Transparent.
This "breaks" if you include a Profile.

Acorn

Thanks Acorn,

I suspect that I once knew this but memory keeps letting me down...