Dot tunnel
A tunnel built from flying points instead of a textured surface — cheap enough for machines with no fill rate.
Rather than covering a surface with texture, the tunnel is drawn as a cloud of points: dots placed on concentric rings along the depth axis and projected with perspective, so they stream past the viewer. Because the effect only plots single pixels instead of filling spans, it ran on machines where the fill-hungry tunnel effect was too expensive.
It's part of the demoscene's basic vocabulary, and was often combined with a starfield or a plasma in the background — the same maths, a different amount of colour per pixel.