Cheat Codes

Keep your score after you lose your lives in single player mode (ineffective in the rooftop level): After getting the game over screen, DO NOT CONTINUE. Instead let the game take you back to the main menu and then choose "Continue Game". You'll start at the beginning of the level that you died on, along with the points that you had when you entered the stage.

Unlock levels for quick play mode: Play story mode and defeat the boss at the end of a level to unlock that stage in quickplay mode.