Thank you. The menu interface was modified from a preexisting handheld console (the "Game Prince RS-1" 152-in-1), and was altered solely through HEX data. As such, you will need the original Game Prince ROM in order to develop a menu based on it. There were several key points that had to be studied surrounding the menu, in addition to standard graphic editing (using programs such as YY-CHR):
*Replacing all games on the original console with the new games, which were pasted in via HEX. This also involves altering the linked areas for each menu option, under the Game Prince menu's custom format for reading games (detailed in the "linked menu studies" section in the attached .txt, from address #05E010 onward).
*Altering the titles in the selection menu. This is fairly easy to edit, but it reads the code in multiple areas of the ROM, and is sometimes out-of-order compared to the numerical list.
*Adjusting the amount of menu entries, since I didn't use all 152 game slots. Note that it's much easier to shorten the game count rather than increase it.
*Changing the color values of the preview images, which is controlled by a line below each preview icon's palette data.
I have attached a .txt that I wrote while studying the menu system, though some parts may be irrelevant or confusing; thus the greater description above.