Building the Options window

Make the following changes in MenuScreen to add the Options window layer:

import com.packtpub.libgdx.canyonbunny.util.CharacterSkin;
import com.packtpub.libgdx.canyonbunny.util.GamePreferences;

private Skin skinLibgdx;

private void loadSettings() {
  GamePreferences prefs = GamePreferences.instance;
  prefs.load();
  chkSound.setChecked(prefs.sound);
  sldSound.setValue(prefs.volSound);
  chkMusic.setChecked(prefs.music);
  sldMusic.setValue(prefs.volMusic);
  selCharSkin.setSelectedIndex(prefs.charSkin);
  onCharSkinSelected(prefs.charSkin);
  chkShowFpsCounter.setChecked(prefs.showFpsCounter);
}

private void saveSettings() {
  GamePreferences prefs = GamePreferences.instance;
  prefs.sound = chkSound.isChecked();
  prefs.volSound = sldSound.getValue();
  prefs.music = chkMusic.isChecked();
  prefs.volMusic = sldMusic.getValue();
  prefs.charSkin = selCharSkin.getSelectedIndex();
  prefs.showFpsCounter = chkShowFpsCounter.isChecked();
  prefs.save();
}

private...