Level select:- Successfully complete the game.
Powered-up ship and torpedo:- Successfully complete the game, and
save. Then, start a new game.
Ghost Ship:- Successfully complete the game two times to unlock the
Ghost Ship at the level selection screen.
10,000 Steels:- Reach the Part 3-7 fight. Talk to the Dock Master and
collect 10,000 Steels from her. Save the game, then go to the Dock Master
again. She will give you 10,000 Steels again. Repeat to get as much as
needed.
Torpedoes:- Get to the final part of the Part 8-15 fight and get a
free Torpedoes at the Torpedo Shop. Collect as many as you can