public void addedToWorld (World w)
    {
        // from 255(transparent) to 0 (opaque), we loop through phase by phase to create fading effect
        for (int fader = 0; fader <= 255; fader += 20)
        {
            fade.setTransparency(fader);
            // delay by 0.02 seconds to create better effect
            Greenfoot.delay(2);
        }
    }