int x1, x2, y1, y2;
  
int boxWidth=250;
int boxHeight=250;
int boxX=100;
int boxY=100;
  
int r=150;
int g=140;
int b=180;

void setup(){
 size(500,500);
}

void draw() {
  // Setup the background.
  fill(0,0,250,10);
  rect(0,0,width,height);
  
  // Setup the motion.
  x1 = int(random(6)-3);
  x2 = int(random(6)-3);
  y1 = int(random(6)-3);
  y2 = int(random(6)-3);
  
  
  // Changing colour assignment.
  r += int(random(4)-2);
  g += int(random(4)-2);
  b += int(random(4)-2);
 
  // Draw the box.
  fill(r,g,b);
  rect(boxX,boxY,boxWidth,boxHeight); 
}

void mouseDragged() {
  // Check if the left mouse button is pressed and do the following.
  if (mousePressed && (mouseButton == LEFT)) {
    boxX = mouseX - (boxWidth/2);
    boxY = mouseY - (boxHeight/2);
    boxWidth += x2;
    boxHeight += y2;
  } 
  // Check if the right mouse button is pressed and do the following.
  else if (mousePressed && (mouseButton == RIGHT)) {
    boxX += x1;
    boxY += y1;
    boxWidth = mouseX;
    boxHeight = mouseY;
  }   
}