The Bouncing Ball

float posX;

float posY;

float velocity;

​

void setup(){

  size(400,400);

  background(255);

  posX=random(40,width-40);//to make the initial position of the ball random.

  posY=random(40,height-40);//to make the initial position of the ball random.

  velocity=2.5;//to control the speed and direction of the ball

  fill(0,0,255);

  smooth();

  }

​

void draw(){

/*There are only two conditions that the ball can have:

one is out of the edges of the window, the other is inside the window. 

  */

  if(posX>=width-40||posX<=40){

    velocity=velocity*(-1);

  }

background(255);

posX+=velocity;

ellipse(posX,posY,80,80);

}