Ball ball1;
Ball ball2;

float gravity = 0.1;

void setup(){
  size(200,200);
  ball1 = new Ball(50,0,16);
  ball2 = new Ball(100,50,32);
}

void draw(){
  background(100,150,20);
  ball1.display();
  ball1.move();
  ball2.display();
  ball2.move();
}

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

  Ball (float tempx, float tempy, float tempd){
    x= tempx;
    y=tempy;
    d=tempd;
    speed=2;
  }

  void display(){
    fill(100,30,250);
    noStroke();
    smooth();
    ellipse(x,y,d,d); 
  }

  void move(){
   y=y+speed;
   speed = gravity+speed;
    if(y>=height){
      speed=speed*-0.95;
    }
  }
}