Processing Project

// needs to install the library ControlP5 through Sketch -> Manage Libraries
// You can find it by just searching "p5"

import java.lang.Math;
import controlP5.*;

ControlP5 cp5;
int rad = 30;
int numBalls = 1500;
int og = numBalls;
int[] dirs = {-1, 1};

class Ball {
  private float x, y, xSpeed, ySpeed;
  private int xDir, yDir, rad;
  private int[] colors;

  Ball(float _x, float _y, float _xSpeed, float _ySpeed, int _xDir, int _yDir, int[] _colors, int _rad) {
    this.x = _x;
    this.y = _y;
    this.xSpeed = _xSpeed;
    this.ySpeed = _ySpeed;
    this.xDir = _xDir;
    this.yDir = _yDir;
    this.colors = _colors;
    this.rad = _rad;
  }

  public void setX(float x) {
    this.x = x;
  }

  public void setY(float y) {
    this.y = y;
  }

  public void setColor(int[] colors) {
    //reset colors
    int[] temp = {};
    colors = temp;

    // add new colors
    this.colors[0] = colors[0];
    this.colors[1] = colors[1];
    this.colors[2] = colors[2];
  }

  public void setSpeed(float xSpeed, float ySpeed) {
    this.xSpeed = xSpeed;
    this.ySpeed = ySpeed;
  }

  public void setXDir(int xDir) {
    this.xDir *= xDir;
  }

  public void setYDir(int yDir) {
    this.yDir *= yDir;
  }

  public void setRad(int rad) {
    this.rad = rad;
  }

  public float getX() {
    return this.x;
  }

  public float getY() {
    return this.y;
  }

  public int[] getColor() {
    return this.colors;
  }

  public int getXDir() {
    return this.xDir;
  }

  public int getYDir() {
    return this.yDir;
  }

  public int getRad() {
    return this.rad;
  }

  public float getXSpeed() {
    return this.xSpeed;
  }

  public float getYSpeed() {
    return this.ySpeed;
  }
}

Ball[] balls;

void setup() {
  initializeBalls(numBalls);
  
  cp5 = new ControlP5(this);

  // Number of Balls Slider
  cp5.addSlider("numBalls")
    .setPosition(width/2, 20)
    .setRange(0, numBalls) // Set the range of values for the slider
    .setValue(numBalls)
    .setLabel("Number of Balls");

  //fullScreen();
  size(800,800);
  noStroke();
  ellipseMode(RADIUS);

  
}

void initializeBalls(int count) {
  int[] b = {0, 0, 0};
  balls = new Ball[og + count];
  for (int j = 0; j < balls.length; j++) {
    balls[j] = new Ball((float) (Math.random() * (width - rad*2) + rad), (float) (Math.random() * (width - rad*2) + rad), random(5, 20), random(5, 20), dirs[(int)(Math.random() * dirs.length)], dirs[(int)(Math.random() * dirs.length)], b, 30);
  }
}

void numBalls(int value) {
  numBalls = (int) value; // Update the numBalls variable with the slider value

  if (numBalls < og) {
    for (int i = og - 1; i >= numBalls; i--) {
      // Reset properties for removed balls
      balls[i].setX(0);
      balls[i].setY(0);
    }
    og = numBalls; // Update the original number of balls
  } else {
    // Add new balls if numBalls is increased
    initializeBalls(numBalls - og);
    og = numBalls; // Update the original number of balls
  }
}


int[] getColor() {
  int[] _color = new int[3];
  int min = 0;
  int max = 255;
  int range = max - min + 1; // Increase range by 1 to include max value

  for (int i = 0; i < 3; i++) {
    _color[i] = (int) (Math.random() * range) + min;
  }
  return _color;
}

void changeColor(int index) {
  balls[index].setColor(getColor());
}

int[] bgCol = getColor();

void draw() {
  background(bgCol[0], bgCol[1], bgCol[2]);

  for (int i = 0; i < numBalls; i++) {
    if (balls[i].getX() > width - balls[i].getRad() || balls[i].getX() < balls[i].getRad()) {
      balls[i].setXDir(-1);
      balls[i].setX(balls[i].getX() + (balls[i].getXSpeed() * balls[i].getXDir()));
      changeColor(i);
    }

    if (balls[i].getY() > height - balls[i].getRad() || balls[i].getY() < balls[i].getRad()) {
      balls[i].setYDir(-1);
      balls[i].setY(balls[i].getY() + (balls[i].getYSpeed() * balls[i].getYDir()));
      changeColor(i);
    }

    balls[i].setX(balls[i].getX() + (balls[i].getXSpeed() * balls[i].getXDir()));
    balls[i].setY(balls[i].getY() + (balls[i].getYSpeed() * balls[i].getYDir()));

    fill(balls[i].getColor()[0], balls[i].getColor()[1], balls[i].getColor()[2]);
    ellipse(balls[i].getX(), balls[i].getY(), balls[i].getRad(), balls[i].getRad());
  }
}