Flies the picture toward you down an endless tunnel. It is a demoscene classic, and there is no 3D in it whatsoever.
The trick is a choice of coordinates. Take the angle around the centre as one axis, and one divided by the distance from the centre as the other. That division is what supplies the perspective. Because dividing turns large numbers small, evenly spaced steps along that axis land closer and closer together as you approach the middle of the screen, which is exactly what evenly spaced rings do when they recede toward a vanishing point. Your eye reads depth into it immediately.
Adding time to that axis flies forward; adding it to the angle rolls the tunnel. shape swaps the round cross-section for a triangle, square, hexagon or octagon. center fades out the vanishing point, which is worth using, because at the exact centre the division goes to infinity and the texture there breaks up.