@Override
 public boolean onOptionsItemSelected(MenuItem item) {
   switch (item.getItemId()) {
     case R.id.preferences_button:
       Intent preferencesIntent = new Intent(this, PreferencesActivity.class);
       startActivity(preferencesIntent);
       return true;
     case R.id.help_button:
       Intent helpIntent = new Intent(this, HelpActivity.class);
       startActivity(helpIntent);
       return true;
     case R.id.credits_button:
       Intent creditsIntent = new Intent(this, CreditsActivity.class);
       startActivity(creditsIntent);
       return true;
     case R.id.donate_button:
       billing.preDonation(this);
     default:
       return super.onOptionsItemSelected(item);
   }
 }