/**
 * Autumn. A world with some leaves.
 * 
 * @author Michael Kölling
 * @version 0.1
 */
public class MyWorld extends World
{
    /**
     * Create the world and objects in it.
     */
    public MyWorld()
    {    
        super(600, 400, 1);
        setUp();
    }
    
    /**
     * Create the initial objects in the world.
     */
    private void setUp()
    {
        addLeaves();
    }
    private void addLeaves()
    {
        addObject(new Block(), 300, 200);
        int i= 0;
        int x=Greenfoot.getRandomNumber(getWidth());
        int y=Greenfoot.getRandomNumber(getHeight());
        while (i<18);
        {
         addObject( new Leaf(),x,y);
        }
    }    
}

import greenfoot.*;

/**
 * A block that bounces back and forth across the screen.
 * 
 * @author Michael Kölling
 * @version 0.1
 */
public class Block extends Actor
{
    private int delta = 2;
    
    /**
     * Move across the screen, bounce off edges. Turn leaves, if we touch any.
     */
    public void act() 
    {
        move();
        checkEdge();
        checkMouseClick();
        
        checkLeaf();
        
        World world = getWorld();
       
        Leaf leaf = (Leaf) getOneIntersectingObject(Leaf.class);
        leaf.turn(9);
        
         if(leaf!= null) 
       { 
          
       }
    }
    
    /**
     * Move sideways, either left or right.
     */
    private void move()
    {
        setLocation(getX()+delta, getY());
    }
    
    /**
     * Check whether we are at the edge of the screen. If we are, turn around.
     */
    private void checkEdge()
    {
        if (isAtEdge()) 
        {
            delta = -delta;  // reverse direction
        }
    }
    
    /**
     * Check whether the mouse button was clicked. If it was, change all leaves.
     */
    private void checkMouseClick()
    {
        if (Greenfoot.mouseClicked(null)) 
        {
            // do this when the mouse is clicked. currently: nothing.
        }
    }
    private void checkLeaf()
    {
      Leaf leaf = (Leaf) getOneIntersectingObject(Leaf.class);
      if (leaf!= null)
      {
      }
      else
      {
          turn (9);
      }
    }
}

import greenfoot.*;

/**
 * A floating leaf that blows across the screen.
 *
 * @author Michael Kölling
 * @version 1.0
 */
public class Leaf extends Actor
{
    private int speed;
    GreenfootImage img1 = new GreenfootImage("leaf-green.png");
    GreenfootImage img2 = new GreenfootImage("leaf-brown.png");
    
    /**
     * Create the leaf.
     */
    public Leaf()
    {
        setImage(img1);
        speed = Greenfoot.getRandomNumber(3) + 1;      // random speed: 1 to 3
        setRotation(Greenfoot.getRandomNumber(360));
    }
    
    /**
     * Move around.
     */
    public void act() 
    {
        if (isAtEdge()) 
        {
            turn(180);
        }
        
        move(speed);
        
        if (Greenfoot.getRandomNumber(100) < 50) 
        {
            turn(Greenfoot.getRandomNumber(5) - 2);   // -2 to 2
        }
    }
    
    /**
     * Change the image to another leaf image. This toggles back and
     * forth between two images.
     */
    public void changeImage()
    {
        if (getImage() == img1) 
        {
            setImage(img2);
        }
        else {
            setImage(img1);
        }
    }
}