createCanvas(500, 500);

​

}

​

function draw() {

  background(0,0,120);

  translate(width/2,height/2);

  spiral();

}

​

function spiral() {

  fill(200,200,0); stroke(200,200,0);

  var r1 = 0,r2 = 0, step=1,spiralwidth=20.0,dw=spiralwidth/250;

  beginShape(TRIANGLE_STRIP);

  for ( var i = 0 ; i < 250 ; i++ ){

    r1 += step;

    spiralwidth -= dw;

    r2 = r1 + spiralwidth;

    var ang = PI/30;

    var r1x = r1*sin(ang*i);

    var r1y = r1*cos(ang*i);

    var r2x = r2*sin(ang*i);

    var r2y = r2*cos(ang*i);

    vertex(r1x,r1y);

    vertex(r2x,r2y);

     }

  endShape();

}