// Learning Processing
  // Daniel Shiffman
  // http://www.learningprocessing.com
  
  // Example 4-5: Using system variables
  void setup() {
    size(200,200);
    smooth();
  }
  
  void draw() {
    background(100);
    stroke(255);
    // frameCount is used to color a rectangle.
    fill(frameCount / 2);
    rectMode(CENTER);
    // The rectangle will always be in the middle of the window 
    // if it is located at (width/2, height/2).
    rect(width/2,height/2,mouseX+10,mouseY+10);
  }
  
  void keyPressed() {
    println(key);
  }