Processing Animation Basic

animation.pde

int NUM = 1000;
PVector location;
PVector velocity;
void setup() {
  size(800, 600);
  frameRate(60);
  colorMode(HSB, 360, 100, 100, 100);
  noStroke();
  location = new PVector(width/2.0, height/2.0);
  velocity = new PVector(random(-10, 10), random(-10, 10));
}
void draw() {
  background(0);
  fill(120, 100, 100);
  location.add(velocity);
  ellipse(location.x, location.y, 10, 10);
  if (location.x < 0 || location.x > width) {
    velocity.x = velocity.x * -1;
  }
  if (location.y < 0 || location.y > height) {
    velocity.y = velocity.y * -1;
  }
}