As far as I can imagine, it is the Xbox engine that was ported to PC. After all the xbox is a cut down PC.
But I think because the Xbox GPU was custom made, there had to be new hlsl shaders created for PC.
But, I don't think Super Happy Fun Fun had any idea about PC graphics. And I certainly believe they never created those Shaders.
If they were capable of programming Shaders, the port wouldn't have been in such a mess in the first place.
I assume all the effects are in the engine waiting, it just needs someone with graphics know-how to create working Shaders. (That's not me btw
)
I will keeping poking the shaders, moving them around to see what I can find
A good thing, if you minimize the game, make some changes and save, the game loads those changes.