[verytrivial]

I remember a 4k demo that used translucent triangles (I think? my brain is showing me circles, so perhaps a fixed set of sizes and fast blit with alpha.) This created moving volumetric light and shadows around some geometric shapes, some pillars I think. Very smeary/ghostly with overdrawn shapes, but the effect was startling given it was on a 486. It didn't render full frames, but moved the model and just kept splatting.