In the library, and source below - a random experiment that evolved into something pretty. It also creates a slightly disturbing optical illusion if you stare at the center for a second or two.

// Endless tunnel of spiraling squares
// Stare at it long enough and optical illusion makes it seem
// like the background is moving too.
//
// MIT License
// Take this code and make something cool!
// 8.25/2021 ZRanger1

var t2;
export var speed = 5;
export var nSquares = 4;
var cosT = cos(0.1), sinT = sin(0.1);

function signum(a) {
return (a > 0) - (a < 0)
}

export var speed = 5;
var timebase;

export function sliderSpeed(v) {
speed = 1+9* v;
}

export function sliderSquarocity(v) {
nSquares = 1+floor(6*v);
}

You also snuck in CrosstownTraffic into the pattern library, which has a lot of potential (and needs more sliders, IMHO, or at least in my local versionâ€¦ IMLV?)

I donâ€™t want to clog up the pattern library with minor variations, but hereâ€™s a quick tweak â€“ thanks to the coordinate transform functions, it only takes one additional line to rotate the squares (and a few more for a UI slider to turn it on and off):

// Endless tunnel of spiraling squares
// Stare at it long enough and optical illusion makes it seem like the background is moving too.
//
// MIT License
// Take this code and make something cool!
// 8.25/2021 ZRanger1
var cosT = cos(0.1), sinT = sin(0.1);
function signum(a) { return (a > 0) - (a < 0); }
export var speed = 5; export function sliderSpeed(v) { speed = 1+9* v; }
export var nSquares = 4; export function sliderSquarocity(v) { nSquares = 1+floor(6*v); }
export var doRotate = 0; export function sliderRotate(v) { doRotate = trunc(v); }
var timebase = 0;
export function beforeRender(delta) {
timebase = (timebase + delta/1000) % 3600;
t2 = time(0.08);
t1 = speed * timebase;
resetTransform();
translate(-0.5,-0.5);
if (doRotate) rotate(PI2*t2);
}
// squared spiral expression adapted from https://www.shadertoy.com/view/4tlfRB
export function render2D(index,x,y) {
x1 = signum(x); y1 = signum(y);
sx = x1 * cosT + y1 * sinT;
sy = y1 * cosT - x1 * sinT;
dx = abs(sin(nSquares*log(x * sx + y * sy) + atan2(y,x) - t1))
hsv(t2 + x*sx + y*sy, 1, dx * dx * dx)
}

Changing the direction and quantum of rotation would also make interesting variationsâ€¦

Okâ€¦ inspired by @pixie, hereâ€™s the fun math toy of the day - a function that can give any 2D pattern n-sided kaleidoscopic reflections. I wrote this a couple of days ago for the Line Dancer pattern (now in the library), and have been plugging it in to random patterns to see what would happen ever since.

// Sets up a kaleidoscope effect - makes the image
// repeat over nSides evenly divided polar "slices" about the center.
// To use, just include this code block in your pattern, and add the line:
// kal(x,y,timebase); x = outx; y = outy;
// to your render2D(). The timebase parameter controls rotation speed.
// you can use any timing value you like.
var outx,outy;
var nSides = 5;
var slice = PI / nSides;
function kal(x,y,timebase) {
var angle = atan2(y, x);
angle = mod(angle, 2.0 * slice);
// uncomment to reflect each slice so they can be tiled
// symmetrically if you like. ymmv.
//angle = abs (angle - slice);
// rotate over time - rotation in polar coords is really
// simple.
angle += PI*timebase;
var d = hypot(x,y);
outx = d * cos(angle); outy = d * sin(angle);
}

and hereâ€™s a version of Tunnel of Squares that uses it, with a â€śReflectionsâ€ť slider.

Tunnel of Mirrors

// Endless tunnel of spiraling squares
// Stare at it long enough and optical illusion makes it seem
// like the background is moving too.
//
// MIT License
// Take this code and make something cool!
// 8.25/2021 ZRanger1
var t2;
export var speed = 5;
export var nSquares = 4;
var cosT = cos(0.1), sinT = sin(0.1);
function signum(a) {
return (a > 0) - (a < 0)
}
export var speed = 5;
var timebase;
export function sliderSpeed(v) {
speed = 1+9* v;
}
export function sliderSquarocity(v) {
nSquares = 1+floor(6*v);
}
export function sliderReflections(v) {
nSides = 1+floor(v * 15);
slice = PI / nSides;
}
// This block of code sets up a kaleidoscope effect - makes the image
// repeat over nSides evenly divided polar "slices" about the center.
// To use, just add the line:
// kal(x,y,timebase / 2); x = outx; y = outy;
// to your render2D(). The timebase parameter controls rotation speed.
// you can use any timing input you like.
var outx,outy;
var nSides = 5;
var slice = PI / nSides;
function kal(x,y,timebase) {
var angle = atan2(y, x);
angle = mod(angle, 2.0 * slice);
// uncomment to reflect each slice so they can be tiled
// symmetrically if you like. ymmv.
//angle = abs (angle - slice);
// rotate over time - rotation in polar coords is really
// simple.
angle += PI*timebase;
var d = hypot(x,y);
outx = d * cos(angle); outy = d * sin(angle);
}
translate(-0.5,-0.5);
export function beforeRender(delta) {
timebase = (timebase + delta/1000) % 3600;
t2 = time(0.08);
t1 = speed * timebase;
}
// squared spiral expression adapted from https://www.shadertoy.com/view/4tlfRB
export function render2D(index,x,y) {
kal(x,y,timebase / 2); x = outx; y = outy;
x1 = signum(x); y1 = signum(y);
sx = x1 * cosT + y1 * sinT;
sy = y1 * cosT - x1 * sinT;
dx = abs(sin(nSquares*log(x * sx + y * sy) + atan2(y,x) - t1))
hsv(t2 + x*sx + y*sy, 1, dx * dx * dx)
}