public synchronized static void initializeImages() 
    {
        if(images == null) 
        {
            GreenfootImage baseImage = new GreenfootImage("explosion-big.png");
            images = new GreenfootImage[IMAGE_COUNT];
            for (int i = 0; i < IMAGE_COUNT; i++)
            {
                int size = (i+1) * ( baseImage.getWidth() / IMAGE_COUNT );
                images[i] = new GreenfootImage(baseImage);
                images[i].scale(size, size);
            }
        }
    }