Bar Button World

import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)

/**
 * Write a description of class MyWorld here.
 * 
 * @author (your name) 
 * @version (a version number or a date)
 */
public class MyWorld extends World
{

    /**
     * Constructor for objects of class MyWorld.
     * 
     */
    
    private Actor valueBar;
    private int value = 50;
    private int minValue = 0;
    private int maxValue = 100;
    
    static final Color TRANS = new Color(0,0,0,0);
    
    Actor btn01,btn02;
        
    public MyWorld()
    {    
        // Create a new world with 600x400 cells with a cell size of 1x1 pixels.
        super(600, 400, 1); 
        valueBar = new SimpleActor();
        updateValueDisplay();
        addObject(valueBar, 400, 100);
              
        addObject(btn01 = getNewButton("BUTTON 01"),200,100);
        addObject(btn02 = getNewButton("BUTTON 02"),200,150);
        
    }
    
    public void adjustValue(int amount)
    {
        value += amount;
        if(Greenfoot.mouseClicked(btn01))
            if(value<minValue) value = minValue;
        if(Greenfoot.mouseClicked(btn02))
            if(value>maxValue) value = maxValue;
        updateValueDisplay();
    }
    
    //public void adjustValue(int amount) 
    //{
    //    value += amount;
    //    if (value<0) value = 0;
    //    if (value>maxValue) value = maxValue;
    //    updateValueDisplay();
    //}   
      
    private void updateValueDisplay()
    {
        int wide = 100;
        int high = 12;
        
        GreenfootImage fullImg = new GreenfootImage(wide, high);
        fullImg.setColor(Color.GREEN);
        fullImg.fill();
        
        GreenfootImage colorBar = new GreenfootImage(wide, high);
        int percentage = wide*value/maxValue;
        colorBar.drawImage(fullImg, percentage-wide, 0);
        
        GreenfootImage img = new GreenfootImage(wide+4, high+4);
        img.setColor(Color.WHITE);
        img.fill();
        img.setColor(Color.BLACK);
        img.drawRect(0,0,wide+3, high+3);
        img.drawImage(colorBar, 2, 2);
        valueBar.setImage(img);
    }
    
    protected Actor getNewButton(String caption)
    {
        GreenfootImage base = new GreenfootImage(400,230);
        base.setColor(Color.BLUE);
        base.fillRect(100,100,200,30);
        
        GreenfootImage text = new GreenfootImage(caption,20,Color.BLACK, TRANS);
        base.drawImage(text,200-text.getWidth()/2,115-text.getHeight()/2);
        base.setTransparency(128);
        
        Actor button = new Actor()
        {
        };
        button.setImage(base);
        return button;
        
    }
}