Nine credits:
Press Up, Up, Down, Down, Left, Right, Left, Right, II, I at the title screen. Up to nine credits may be selected through the options menu.

Ten ships:
Press Up, Up, Down, Down, Right, Left, Right, Left, I, II on controller two at the title screen. Up to ten ships may be selected through the options menu.

Arcade mode:
Press I, II, Right, Left, Right, Left, Down, Down, Up, Up on controller three at the title screen. Then, select "Vmode" on the options menu.

Level select:
Press Up, Right, Down, Left, Down, Right, I, II, Left on controller four at the title screen.

View animation sequences:
Press Up, I, Right, II, Down, I, Left, II, Up, Select on controller five at the title screen.