So I've been using paint.net for a whole now to crop and make clear backgrounds on images and layer them with others. As of late I've decided to take on a more ambitious project: to make an animated gif of a starship using a tractor beam to drag an object into the center of a picture and then leave. I am in the process of searching the forums as how to make an animated gif, and I would like to know how to create a sort of tractor beam effect. It doesn't have to be realistic (as the images I'm using are slightly cartoonish), but enough to look like a blue beam of light is shining (but gradually getting weaker) onto an object.
To put it simply, I need it to look like there's a blue light shining downwards onto on onbject.
Thanks!
EDIT: I just want to add that the light will be directed downward, there will not be any 3d effects in the picture I want to create.