Enter the following code at the Title Screen: A + B + C - Start A new option should appear allowing you to practice on any level.

To earn 200,000 points when you battle any boss (except Stavros) reduce your foe to within a flame or two of destruction, then stay out of reach until the last ten seconds. At the very last second, use ninja magic to destroy the boss.

In the bonus round where you have to shoot the ninjas, you can either kill none or all ninjas. This will give you an extra life.