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

void draw() {
  //do some drawing
  background(0);
  
  int x1, x2, y1, y2;
  
  int boxWidth=250;
  int boxHeight=250;
  int boxX=100;
  int boxY=100;
  
  x1 = int(random(6)-3);
  x2 = int(random(6)-3);
  y1 = int(random(6)-3);
  y2 = int(random(6)-3);
  
  boxX += x1;
  boxY += y1;
  boxWidth += x2;
  boxHeight += y2;
 
  fill(255,0,0);
  rect(boxX,boxY,boxWidth,boxHeight); 
}




// line(x1,y1,x2,y2);

//first two coordinates are the top left corner (the origin)