class Ball {
  
  float x, y;
  float rayon;
  color coul;
  float vitx = random(0, 2)-1;
  float vity = random(0, 2)-1;
  float vitRayon = random(0, 2);
  
  Ball(){
    x = random(width);
    y = random(height);
    rayon = random(1, 40);
    coul = randCoul();
  }
  
  void drawBall(){
    
    rayon += vitRayon;
    if(rayon>60 || rayon<1){
      vitRayon *= -1; 
    }
    rayon = max(1, rayon);
    
    noStroke();
    
    vitx += (random(0, 2)-1)/5;
    vity += (random(0, 2)-1)/5;
    
    // zone de travail circulaire
    float distRef = dist(x, y, width/2, height/2);
    if(distRef>limiteDist){
      // si on dépasse on retourne petit à petit la vitesse
      float distx = width/2-x;
      float disty = height/2-y;
      vitx += distx/distRef;
      vity += disty/distRef;
    }
    
    x += vitx;
    y += vity;
      
    fill(coul);
    ellipse(x, y, rayon, rayon);
  }
  
}

int nbBalls = 60;
Ball[] boule = new Ball[nbBalls];
// ça c'est un tablo, mais il y a les arrayList qui sont mieux...

float limiteDist = 400;

void setup(){
 smooth();
 size(640, 480); 
 //size(screen.width, screen.height);
 
 colorMode(HSB, 100, 100, 100);
 
 for(int i = 0; i<nbBalls; i++){
   boule[i] = new Ball();
 }
 frameRate(40);
}

void draw(){
  background(100, 0, 100);
  for(int i = 0; i<nbBalls; i++){
   boule[i].drawBall();
 }
}

// in setup : colorMode(HSB, 100, 100, 100);
int baseCoul = round(random(0, 100));
color randCoul(){
  // Hue / Sat / Bright
  return(color(baseCoul, round(random(30, 70)), round(random(10, 100))));
}