gistfile1.txt

Particle p;

void setup() {
  size(500, 500);
  background(255);
  p = new Particle(width*0.5, height*0.5, 1);
}

void draw() {
  background(255);
  p.draw();
}

class Particle extends PVector {
  Particle(float x, float y, int whatever) {
    this.x = x;
    this.y = y;
  }
  void draw() {
    pushMatrix();
    translate(this.x, this.y);
    ellipseMode(RADIUS);
    ellipse(0, 0, 20, 20);
    popMatrix();
  }
}