I have a code that makes little spheres appear at the top of the screen and then they shake as they fall down. I want to change the code so that the balls appear one at a time and once one ball reaches the bottom the next one comes up.

 

final int maxAsteroid=20;
int[] xAsteroid = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
int[] yAsteroid = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
int[] tempAsteroid = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
int a;
boolean[] AsteroidActive = {true,true,true,true,true,true,true,true,true,true,true,true,true,true,true,true,true,true,true,true};

void setup(){
  size(750,300);
  noStroke();
  smooth();
  for (int i=0; i<maxAsteroid; i++){
    xAsteroid[i]=int(random(10,740));
    AsteroidActive[i]=(random(2)<1);
  } 
}

void draw(){
  background(150);
  for (int i=0; i<maxAsteroid; i++){
    for(int ii=0; AsteroidActive[ii] == true; ii++ ){
      ellipse(xAsteroid[i],yAsteroid[i],15,15);
      if(yAsteroid[i]<250){
        yAsteroid[i]=yAsteroid[i]+1;
        xAsteroid[i]=xAsteroid[i]+int(random(0,5))-int(random(0,5));
      }
    }
  }
}