var radius = 1;

​

function setup() {

  createCanvas(400, 400);

  background(220);

  stroke(0,0,0,100);

  noFill();

  center = createVector(width/2,height/2)

}

​

function draw() {

  circle(center.x,center.y,radius);

  center.x += random(-2,2);

  center.y += random(-2,2);

  radius += random(1);

}