Canvas.setpenopacity(-0.25);

const turtle = new Turtle();
const sf = 0.01;
const iters = 100000;
let x, y, sx, sy, i, j, si, sj, sine, len, l;

function walk(i) {
    x = -110+220*Math.random();
    y = -110+220*Math.random();
    sx = 0.75-sf*(100+x)*0.2;
    sy = 0.4+sf*(100+y)*0.15;
    sine = (Math.sin(-2*Math.E*sx+2*Math.sin(sy))
          - Math.cos(1-Math.sqrt(2)*sy+2*Math.cos(sx)))
          * Math.sin(3*Math.acos(sx)*Math.asin(sy))
          * Math.cos(-3*Math.asin(sx)*Math.acos(sy))
    turtle.penup();
    turtle.goto(x,y);
    turtle.seth(sine*360+90);
    turtle.pendown();
    len = 8+4*sine;
    for (l = len; l > 0.5; l/=2) {
        turtle.forward(l);
        turtle.left(30*sine);
    }
    return i < iters;
}