Mode Add Site: Insert site with left mouse button, using the selected weight. Remove site with right mouse button.
Mode Change Radius: Increase weight with left button, decrease with right button (click near the site but not on the site).
In both modes you can move (drag) a site with the left or right mouse button.
Applet by Oliver Münch, Diploma Thesis at FernUniversität Hagen, 1998.