[Inkscape-user] Fill and stroke dialog - radial gradients usage

Hello everybody,

new to Inkscape I'm tring to use the Fill & stroke dialog, tab "Fill" => Radial gradient and whish to fill some rectangle with some color - but not evenly.

I can get center darker than periphery but I'd like to get center lighter than periphery instead, and don't know how to do that.

I tried to play withe those blue and red squares in the central zones but I hardly understand : - what is their exact usage - how to move each square separately - what those blue lines stand for and how to use it.

I've similar questions for linear gradient.

I'm an absolute newbee in drawing as in Inkscape's usage, so please be patient and excuse my bad English -- But feel free to answer in French

Regards,

Didier Spaier Paris