I think the Balatro background is a shader but the technique and effect it gives are different - this one has a static "ring" that shrinks as it moves inward to

I think the Balatro background is a shader but the technique and effect it gives are different - this one has a static "ring" that shrinks as it moves inward to the horizon, the Balatro one has a fluid motion to it. The Balatro background reminds me (intentionally, I suspect) of demoscene effects, I love it