import greenfoot.*;

public class game3 extends World
{
    private static final String bgImageName = "watergoed.jpg";
    private static final int scrollSpeed = 2;
    private static final int picHeight = (new GreenfootImage(bgImageName)).getHeight();
      
    private GreenfootImage bgImage, bgBase;
    private int scrollPosition = 0;
    
    public game3()
    {    
        super(900, 900, 1); 
        setBackground(bgImageName);
        bgImage = new GreenfootImage(getBackground());
        bgBase = new GreenfootImage(getWidth(), picHeight);
        bgBase.drawImage(bgImage, 0, 0);
        // prepare();
    }
      
    public void act()
    {
        scrollPosition += scrollSpeed;
        while(scrollSpeed > 0 && scrollPosition > picHeight) scrollPosition -= picHeight;
        while(scrollSpeed < 0 && scrollPosition < 0) scrollPosition += picHeight;
        paint(scrollPosition);
    }
    
    private void paint(int position)
    {
        GreenfootImage bg = getBackground();
        bg.drawImage(bgBase,0, position);
        bg.drawImage(bgImage,0 , position-picHeight);
    }
}