Hudson's Adventure Island II (Game Boy)

Debug Mode


Apply the above patch to a Japanese v1.0 ROM. At the title screen, press B to enter the debug mode (only available with patch). Next to the word Password on the title screen a two-digit hex number will appear. Using D-Pad buttons, you can change number value, and run an option corresponding to this number by pressing Start. Press B to be invulnerable during gameplay. Press Select to exchange the in-game pause menu for a reset to title screen when pressing Start. Both buttons will play jingles. To return to the regular title screen, press A (only available with patch).

Numbers, , , , , and everything above or equal to  is filtered from input, except.

Test Menu


Set number to enter the Test Mode menu. All messages are in standard ASCII encoding, but due to lack of font data, there is no regular display on this menus. The patch above fixes this issue by reorganizing the title screen data. This likely means that the early title screen used regular ASCII before the logo was finalized.

There are three options available in this menu: the first is a Tileset Test, the second is an Object Test and the third is a Sound Test. Fourth menu option has no functionality.

Tileset Test


Select the tileset number with D-Pad buttons, then press A. Choosing an out-of-bounds index will crash the game. Some tilesets use more tiles than there is space available, so they will overwrite the border. Press Start to return to the Test Menu.

Object Test


Select the object by pressing D-Pad then press Select to display it. While an object is shown, press Left or Right to select animation phases for the current object. Press Select to return to the object selection mode. Press Start while in object selection mode to quit to the Test Menu.

All objects have a constrained number of animations. However, particularly for the player sprite, invalid animations can be selected - which will crash the game.

Sound Test


Select the sound effect/music tune with the D-Pad and press A to play it. To stop the music, select and press A. The first 64 entries are sound effects, while the music starts with index.