How can I make a material that is transparent at the center and emission at the corners of a plane I want to get this material that works similar to the Layer weight shader, but I can't get the effect I want.
I want to have a plane that is largely transparent with emission boundaries.  I have attached a diagram that shows the basic idea, along with a basic idea of what shader basis I have going.  This material needs to work well with a non-square plane.  The sphere needs to be able to be stretched/manipulated to fit any shape, even if that means one side of the ellipse is wider than the other side.
PS I'm using EVEE.
Some function of (distance from object origin) will give you a circle to do what you want with.. here, using a Map Range to soften the mask, which is plugged into the alpha-channel of an emissive material. If you need to have the center of the circle somewhere else, you could use another object's origin, using the option near the bottom of the Texture Coordinate node.