int x = 75;
int y = 60;
int d = 5;
int shift = 2;

int numCircles = 2000;
int [] xArray = new int[numCircles];
float [] yArray = new float[numCircles];
float [] speed = new float[numCircles];

void setup() {
  size(1200, 800);
  smooth();
  background(0);
  for (int i = 0; i < xArray.length; i++) {
    xArray[i] = x + i * shift;
    yArray[i] =  random(y - 10, y + 11);
    speed[i] = random(7.9, 19.1);
  }
  
  // frames per second -- default is 60
  // frameRate(2); 
  
}


void draw() {
  background(0);
  for (int i = 0; i < xArray.length; i++) {
    ellipse(xArray[i], yArray[i], d, d);
    yArray[i] = yArray[i] + speed[i];
    if (yArray[i] > (height + d/2))
      yArray[i] = - (d/2);
  }
}