var colorg = 0;

var colorb = 255;

​

function setup() { 

  createCanvas(windowWidth, windowHeight);

} 

​

function draw() { 

  //background(220);

    if (dist(mouseX, mouseY, width/2,height/2) < (300-i*30)/2) {

    background(0);

  } else {

    background(255);

  }

    stroke (255,100);

    background(255);

    for(var i =0; i<10;i++){

    fill(colorr, colorg, colorb-i*20);

    ellipse(width/2,height/2,300-i*30,300-i*30);

            ellipse(width/4,height/4,300-i*30,300-i*30);

                ellipse(width-200,height/5,300-i*30,300-i*30);

        }

}