Bonus difficulty settings
 
 Successfully complete the game on the "Easy" difficulty setting to
 unlock the "Normal" difficulty setting. Successfully complete the
 game on the "Normal" difficulty setting to unlock the "Hard"
 difficulty setting. 
 
 Model mode
 
 Successfully complete the game on the "Easy" and "Normal" difficulty
 settings. 
 
 Sound test
 
 Successfully complete the game on the "Easy", "Normal", and "Hard"
 difficulty settings.