I will write a custom shader you tune yourself, in unity, unreal, hlsl or glsl

The hard part of a shader brief is almost never the maths. It is that "subtle and alive" is a taste, not a spec, and on a fixed price that becomes an unbounded argument.

So I build it parameterised from the start. Colour ramp, intensity, speed, spread, falloff: the ones you name become sliders in your inspector. You dial the feel yourself in real time instead of describing it to me and waiting a day for the next version. A disagreement about taste becomes a number you drag, and a second variant is a preset when the dials I exposed reach it.

One order is one effect, and it is shader code only: no meshes, textures, or VFX systems. The source comes with it, written in your engine's conventions. If the effect costs more frame time than it is worth on your target device, I say so before you pay.

Twenty years of graphics and engine work. Unity HDRP and URP, Unreal, raw HLSL and GLSL, WebGL and WebGPU. On a 2026 HDRP contract I shipped a procedural screen space effect as dials, and the client tuned the final look himself, with no further iteration round.

Tell me the effect and the engine, and send a reference image if you have one.