bouncing ball

int xPos;

int yPos;

int velocity;

​

void setup() {

  size(400, 400);

  background(177, 4, 203);

  xPos=int(random(200, 200));

  yPos=int(random(20, height-20));

  velocity=4;

}

​

void draw() {

  background(177, 4, 203);

  yPos=yPos+velocity;

  if (yPos<=20||yPos>=width-20) { 

    velocity=velocity*(-1);

  }

​

  fill(250, 255, 0);

  noStroke();

  smooth();

  ellipse(xPos, yPos, 50, 50);

}