Them circles

circles.pde

class Circle {
  PVector center;
  float radius;
  
  public Boolean intersects(ArrayList<Circle> circles) {
    for(Circle other : circles) {
      if(this.center.dist(other.center) <= (other.radius + this.radius)) {
        return true;
      }
    }
    return false;
  }
}


int ncircles = 20000;
float rx = -1, ry = -1;

ArrayList<Circle> circles = new ArrayList<Circle>(ncircles);

void setup() {
  //size(1200, 600);
  fullScreen();
  initCircles();
}

void initCircles() {
  circles.clear(); 
  
  for(int i=0;i<ncircles;i++) {
    Circle c = new Circle();
    c.center = new PVector(random(width), random(height));
    c.radius = random(60);
    
    while(c.intersects(circles)) {
      c.radius -= 0.5; 
    }
    if(c.radius > 1) {
      circles.add(c);
    }
  }
}

void mouseMoved() {
  if(rx < 0) {
    rx = mouseX;
    ry = mouseY;
  }
}

void draw() {
  background(255);
  noStroke();
  fill(0);
  
  for(Circle c : circles) {
    ellipse(c.center.x - ((rx-mouseX) * (c.radius  / 128)), 
    c.center.y - ((ry-mouseY) * (c.radius / 128)), 
    2 * c.radius, 
    2 * c.radius);
  }
}