float a = 0;
float RL;
int i;

void setup()
{
  size(200, 200);
  colorMode(RGB);
  background(151,151,255);
  stroke(255);
}

void loop() {
  for(i=0; i<(mouseX*4); i++){
    drop1();
  }
}

void drop1(){
  a = (random (10) + mouseY/10)/5 + a;
if (a > height) { a = random(height/2)-50; }
  RL = random(200);
  line(RL, a, RL, a+(mouseY/10));
}