Move Rectangle In Processing Using LightBlue Bean

import processing.serial.*;

// Object to read from the serial port
Serial myPort;

// variables to store the accelerometer coordinates
int ax, ay, az;

// rectangle X position, Y position, Width and Height
int x, y, w, h;

void setup() {
  
  // rectangle size (position will be defined dinamically)
  w = 50;
  h = 100;
  
  // set canvas size. Because sensors read from -255 to 255, will need to add
  // 255 to the value (to avoid negative positions). So values will be converted 
  // to 0 - 510, and considering the rectangle dimensions, this is the appropriate
  // size for the canvas (510 + w, 510 + h)
  size(560, 610);
  
  // communication with the lighblue bean
  myPort = new Serial(this, "/tmp/cu.Lightblue-Bean", 57600);
  

  
  // rectangle color
  fill (250, 200, 0);

}

void draw() {
  
  while (myPort.available() > 0) {
    
    // read from serial
    String value = myPort.readString();
    
    // if it is not empty, process it
    if (value != null && value.length() > 4) {
      String[] sensors = value.split(",") ;
      ax = Integer.parseInt(sensors[0].trim());
      ay = Integer.parseInt(sensors[1].trim());
      az = Integer.parseInt(sensors[2].trim());
      
      // Sensor values goes from -255 to 255, so we need to add 255 and divide
      // by 2 to convert into values from 0 to 255, and use for colors
      int gray = (az + 255) / 2;
      
      // change background to reproduce Z axis variation
      background (gray, gray, gray);
      
      // as we don't have negative position, need to add 255 (so it will
      // be from 0 to 510)
      x = ax + 255;
      y = ay + 255;
      
      // draw the rectangle
      rect (x, y, w, h);
      
      // A little pause to avoid lag
      delay (50);
      
    }
    
  }
}