Harmonograph
Harmonographs are actually mechanical apparatus used to create geometric imagery using pendulums.
But instead of a actual pendulums, we use equations to simulate the motion of pendulums to create harmonographs.
Code
elem=document.querySelector(".example-container");
setCanvas(elem);
a=2;
points=[];
t=0;
function draw(){
clearCanvas();
x=100*cos(degToRad(t))*cos(a)-100*sin(degToRad(t))*sin(a);
y=150*cos(degToRad(t))*sin(a)+500*sin(degToRad(t))*cos(a);
points.push([WIDTH/2+x,HEIGHT/2-y]);
new polygon(points,'#695fe6',0,'#695fe6',0.3,false);
t+=0.005;
a+=0.01;
requestAnimationFrame(draw);
}
draw();