void setup()
{
  size(600, 600);
}

void draw()
{
  background(0);

  PVector c = new PVector(width / 2, height / 2);

  ellipseMode(RADIUS);
  noStroke();

  fill(255, 0, 0);
  ellipse(c.x, c.y, 250, 250);

  fill(0, 255, 0);
  ellipse(c.x, c.y, 200, 200);

  fill(0, 0, 255);
  ellipse(c.x, c.y, 150, 150);

  float a1 = TWO_PI * frameCount / 300;
  float r1 = 225;
  fill(255);
  ellipse(c.x + cos(a1) * r1, c.y + sin(a1) * r1, 25, 25);

  float a2 = TWO_PI * frameCount / 200;
  float r2 = 175;
  fill(0);
  ellipse(c.x + cos(a2) * r2, c.y + sin(a2) * r2, 25, 25);

  float a3 = TWO_PI * frameCount / 100;
  float r3 = 125;
  fill(255);
  ellipse(c.x + cos(a3) * r3, c.y + sin(a3) * r3, 25, 25);
}