var tadd = 0.0;

​

function setup() {

  createCanvas(500,500); //(windowWidth, windowHeight);

  print("(click canvas window and ) use [+] or [-]");

}

​

function draw() {

  background(150,cgreen, 0);

  stroke(0, 0, 150);  strokeWeight(3);  noFill();

  translate(width/2,height/2);

  beginShape();

  for (var t = 0; t < drawsteps *TWO_PI; t += PI/2+tadd) {

    curveVertex(t * cos(t),t * sin(t));

  }

  endShape();

}

​

function keyPressed(){

  if ( key == '+' ) { tadd = 0.015; cgreen = 150;}

  if ( key == '-' ) { tadd = 0.0;  cgreen = 0;}

}