// Learning Processing
  // Daniel Shiffman
  // http://www.learningprocessing.com
  
  // Example 5-3: Rollovers
  void setup() {
    size(200,200);
  }
  
  void draw() {
    background(255);
    stroke(0);
    line(100,0,100,200);
    line(0,100,200,100);
    
    // Fill a black color
    noStroke();
    fill(0);
  
    // Depending on the mouse location, a different rectangle is displayed.    
    if (mouseX < 100 && mouseY < 100) {
      rect(0,0,100,100);
    } else if (mouseX > 100 && mouseY < 100) {
      rect(100,0,100,100);
    } else if (mouseX < 100 && mouseY > 100) {
      rect(0,100,100,100);
    } else if (mouseX > 100 && mouseY > 100) {
      rect(100,100,100,100);
    }
  }