• Use setBackground() to change the color of the sky to light blue.
• Use the sun sprite, sun-4.png.
• Use setScale() to make the sun big.
• Use the layer parameter when enlisting your Entities.

Read about setBackground, setXVelocity, setActive, and setScale.

• Add a mouse listener to your Controller:

public Exercise2B() {
  setTitle("Exercise 2B");
  addMouseListener(this);
  addKeyListener(this);
}

• Code the event handler:

@Override
public void mouseReleased(MouseEvent e) {
	balloon = new RedBalloon(e.getX(), e.getY());
	balloon.setTimeToLive(); // add your parameter here
    addEntity(balloon);
	balloon.setActive(true);
}

• Use setTimeToLive to make the balloon exist for a short time.

Read about MouseListener, .getX, and setTimeToLive.

• Set the balloon's x and y destination in its constructor.
• Code the vector dynamics calculations in the updateParameters method. Review the simulation calculations for help.
• Set the random x and y position, speed, and scale of the balloon in the enlistEntities method:

@Override
protected void enlistEntities() {
	Random rand = new Random();

	// generate random locations within acceptable range
	x = // use rand here
	y = // use rand here

	balloon = new RedBalloon(x, y, centerX, centerY);
	balloon.setScale();
	balloon.setSpeed();
	balloon.setActive(true);
	addEntity(balloon);
}

Read about Random, Math.atan2, and getXLocation, and getYLocation.

• Call notifyController() when the balloon gets to the center, then code the onMessagesPolled to handle the message from the balloon.
• Here's a sequence diagram:

• Here's an idea of how to code the onMessagesPolled method:

@Override
	protected void onMessagesPolled(MessageEvent[] events) {

		for (MessageEvent me : events) {
			String msg = me.getDescription();
			EntityModel em = me.getSender();
			if (msg.equals("centered") && em instanceof RedBalloon) {

				// make the pop sound here
        
                // cast the model as a balloon
				RedBalloon balloon = (RedBalloon) em; 

				// remove the balloon here

				int x = balloon.getX();
				int y = balloon.getY();
				Explosion exp = new Explosion(x, y, 0);

				// setGhost, setScale, etc. as needed
        
				addEntity(exp);	
			}
		}
	}

• Use setGhost(true) on the pop to prevent a collision event being generated when the Explosion sprite and the balloon sprite intersect!

Read about notifyController, onMessagesPolled, .getDescription, .getSender, SoundEffects, removeEntity, and setGhost.