Ball ball1;
Ball ball2;

float gravity=0.1;

void setup(){
  size(200,200);
  smooth();
 
  ball1=new Ball(50,0,16);
  ball2=new Ball(100,50,32);
}
void draw(){
background(255);
ball1.display();
ball1.move();
ball2.display();
ball2.move();
}

class Ball{
float x;
float y;
float speed;
float w;

Ball(float tempX,float tempY,float tempW){
  x=tempX;
  y=tempY;
  w=tempW;
  speed=0;
}

void display(){
  rectMode(CENTER);
  stroke(0);
  rect(x,y,w,10);
}
void move(){
  y=y+speed;
  speed=gravity+speed;
  if(y>height){
    speed=speed*-0.95;
  }
}
}