Archer Maclean's Mercury
This game is titled Archer Maclean's Mercury in North America and Europe and Hg: Hydrium in Japan.
Select two player mode, then enter hg? as your
initials. Return to the main menu and start a single player game.
At the world selection screen, hold L + R and press
Select. All levels will now be unlocked. To lock all levels
again, hold L + R and press Select again.
Get the top high score in each level in a world to
unlock that world's bonus levels.
Strategy guides from GameFAQs