UPDATE: Building off the work that Kent Hansen (aka SnowBro) did many years ago, Nick Mikstas (aka Dirty McDingus) disassembled the entire Metroid code into nine different text files and documented the majority of it far more extensively than SnowBro had. There are descriptions for the title page, intro, ending, password, and music (included within each page). The program can now be edited and reassembled using Ophis. All files are collected here into a single ZIP. We at the MDb hope that this will lead towards many new and creative patches for the original Metroid! Below are the individual text documents:

[Brinstar] | [Definitions] | [Game Engine] | [Game Graphics] | [Kraid] | [Norfair] | [Ridley] | [Title] | [Tourian]


[Download SnowBro’s Code]

Many years ago, an emulation hobbyist and ROM hacker by the name of Kent Hansen (aka SnowBro) set out to gain an intuitive understanding of the inner workings of the software we lovingly refer to as Metroid. Using only a ROM file and his understanding of computer science, he managed to not only separate the ROM file into the assembly code you see below, but was also able to learn how the game engine worked.

From his understanding of the Metroid engine was born the ever-famous MetEdit, a pioneer in the ROM-hacking, level-editing community today.

You may use the X816 Assembler (available here from in order to assemble this code. We (the editors of the MDb) are not personally involved with this project, so we cannot answer any questions related to it!