Sub-Screen Menu:
To access a secret sub-screen, while playing, just press either the A or B buttons on controller 2, this will bring you to a sub-screen menu. Once in the sub-screen, use controller 1 to move the heart-shaped cursor down or up with the directional button, and press the A button to confirm your choice. Options within this menu are:
Reset - resets everything within the current room, so you can try again (you lose one of your lives using this option)
Back - if you open the wrong door, you can start over again from the previous room (you lose one of your lives using this option)
Game - closes the menu without doing anything, returning you to your current game (the instruction manual for this game tells you that it resets the entire game, this is a mistake)