I am looking for a simple "fill and empty" material (see attachment) that just fills a solid colour from bottom to top and back to the bottom. The speed with which it fills and empties as well as the colour should be controllable. I am sure it is simple to code, but I am not a programmer and I couldn't get Bing Chat to write it for me! I tried to modify the "Line Anim" and "Fill" materials which were the closest I could find, but couldn't get either to do what I want.
The scenario is a set of LED strings that I want to appear to fill and empty with a coloured light. i.e. the bottom LEDs should almost always be on and the topmost ones rarely on. I would then drive the colour and speed with MM controls on a set of such LED strings.