Ball ball1;

Ball ball2;

float accel = 0.1;//acceleration - only global variable

void setup() {

  size(800,800);

  ball1 = new Ball(50,0,3,16);

  ball2 = new Ball(100,50,5,32);

}

void draw() {

  background(100);

  ball1.display();

  ball2.display();

  ball1.reflect();

  ball2.reflect();

}

class Ball {

  float x;//horizontal position of ball

  float y;//vertical position of ball

  float xspeed;//horizontal speed of ball

  float yspeed;//vertical position of ball

  float w; //size of ball

  Ball(float tempx, float tempy, float tempxspeed, float tempw) {

    x = tempx;

    y = tempy;

    xspeed = tempxspeed;

    w = tempw;

    yspeed = 0;//initial yspeed always zero, not required as parameter

  }

  

  void display() {

    ellipse(x,y,w,w);

    x = x + xspeed;

    y = y + yspeed;

    yspeed = yspeed + accel;

  }

  

  void reflect() {

    if (y > height) {

      yspeed = yspeed * -0.95;

    }

    if (x < 0 || x > width) {

      xspeed = xspeed * -1.0;

    }

  }

}