class WritableTiledMap extends TiledMap {

    public void setBackgroundColor (String bgColor) {
        if (!bgColor.startsWith("#")) {
            throw new IllegalArgumentException("background color has to start with '#'!");
        }

        if (bgColor.length() < 7) {
            throw new IllegalArgumentException("background color has to min. 7 characters, e.q. '#0000FF' or '#AARRGGBB'");
        }

        this.bgColor = bgColor;
    }

}