When the game over screen appears enter the following command to continue where you left off.
Hard Mode
Play the game, get a high score and get a game over. Do this five times. At the name entry screen input the same name all 5 times. When the hi-score list is populated by the same name, the game will be in hard mode.
Sound test
At the title screen enter the following code to access the sound test.
Unlimited Continues
When entering your initials on the scoreboard enter 68K and you'll have unlimited continues as long as you don't change it.
