class Canvas
{
  float cRadius = width/2.1; // radius of large circle
  float cx = width/2;        // center of large circle
  float cy = height/2;       // center of large circle
  
  Canvas()
  {
    fill(20);
    ellipseMode(CENTER);
    ellipse(cx,cy,cRadius*2,cRadius*2);
  }
}