Ball[] balls;
Vect2D[] vels;
PFont font;

void setup()
{
  size(800, 450);
  frameRate(30);
  
  // load fonts
  font = createFont("myfont.ttf", 10);

  smooth();
  noStroke();
  
  balls = new Ball[100];
  vels  = new Vect2D[100];

  for (int i = 0; i < 100; i++) {  
      float x = random(0, width);
      float y = random(0, height);
      float r = random(5, 40);
      balls[i] = new Ball(x, y, r, "Label Here");
    
      float vx = random(-0.2, 0.2);
      float yx = random(-0.2, 0.2);
      vels[i]  = new Vect2D(vx, yx);
  }
}

void draw()
{
  background(#333333);
  
  for (int i = 0; i < 100; i++) {
    fill(#777777, 170);
    noStroke();
    balls[i].x += vels[i].vx;
    balls[i].y += vels[i].vy;    
    ellipse(balls[i].x, balls[i].y, balls[i].r*2, balls[i].r*2);
    
    // text label
    fill(255);
    textAlign(CENTER);
    textFont(font);
    textSize(balls[i].r * 0.4);
    text(balls[i].artist, balls[i].x, balls[i].y);
    checkBoundaryCollision(balls[i], vels[i]);
  }
  
  // fps display
  textAlign(LEFT);
  textSize(12);
  fill(255); 
  text("fps: " + frameRate, 10,14); 
}


void checkBoundaryCollision(Ball ball, Vect2D vel){
  if (ball.x > width-ball.r){
    ball.x = width-ball.r;
    vel.vx *= -1;
  } 
  else if (ball.x < ball.r){
    ball.x = ball.r;
    vel.vx *= -1;
  } 
  else if (ball.y > height-ball.r){
    ball.y = height-ball.r;
    vel.vy *= -1;
  } 
  else if (ball.y < ball.r){
    ball.y = ball.r;
    vel.vy *= -1;
  }
}

class Ball {
  float x, y, r;
  String artist;  

  // default constructor
  Ball() {
  }

  Ball(float x, float y, float r, String artist) {
    this.x = x;
    this.y = y;
    this.r = r;
    this.artist = artist;
  }
}

class Vect2D{
  float vx, vy;

  // default constructor
  Vect2D() {
  }

  Vect2D(float vx, float vy) {
    this.vx = vx;
    this.vy = vy;
  }
}