myCircle ball;

void setup(){
  size(200, 200);
  ellipseMode(CENTER);
  fill(255);
  ball = new myCircle(width / 4, height / 2, 1, 1, width/20, 1.05);
}

void draw(){
  background(0);
  ball.display();
}

class myCircle{
  int xDir, yDir;
  float speed, diam, xPos, yPos;

  myCircle(float x, float y, int xDir, int yDir, float dia, float velocity){
    xPos = x;
    yPos = y;
    this.xDir = xDir;
    this.yDir = yDir;
    diam = dia;
    speed = velocity;
  }

  void display(){
    if(xPos <= 0 + (diam/2) || xPos >= width - (diam/2)){
      xDir *= -1;
    }

    if(yPos - (diam/2)<= 0 || yPos >= height - (diam/2)){
      yDir *= -1;
    }

    xPos += speed * xDir;
    yPos += speed * yDir;
    ellipse(xPos, yPos, diam, diam);
  }
}