Super Mario Bros. 2, Discombobulated

A disassembly of Super Mario Bros. 2.

This project is intended to fully disassemble, comment, and understand everything about the game Super Mario Bros. 2 on the NES. In addition to the disassembly, there is also documentation about the game's formats, though those are more of a work in progress than the disassembly.

As an added bonus, a fully understood disassembly will also make modifying and changing the game easier!

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Building

This is designed for use with asm6f. For your convenience, binaries of that have been included. (Windows/Linux)

Windows

Open a command prompt window and run:

build           (builds PRG0)
build -dREV_A   (builds PRG1)
build -dSM_USA  (builds Super Mario USA)

This will build the ROM from the assembly, and print any errors in the process. It will then output the SHA-256 hashes of PRG0 and PRG1, as well as the SHA-256 hash of the assembled ROM, useful if you intend to keep a one-to-one build.

Linux, etc

A version of asm6f built under Ubuntu has been included under tools/. To build, run the following command:

./build.sh           (builds PRG0)
./build.sh -dREV_A   (builds PRG1)
./build.sh -dSM_USA  (builds Super Mario USA)
./build.sh test      (builds both PRG0 and PRG1, verifying they match)

The build script will also display a message if the built ROM's SHA-256 hash matches either PRG0 or PRG1.

Output

The build process will generate a few files:

• bin/smb2.nes, your assembled ROM.
• bin/smb2.lst, the assembler listing. Use this to see how the code assembled.
• bin/assembler.txt, the log from the assembler
• bin/smb2.*.nl, name-listing files for FCEUX's debugger.
• Some other cruft, probably. welp

By default, the build script will create a byte-for-byte copy of the game, matching these two SHA-256 hashes:

• PRG0: 47ba60fad332fdea5ae44b7979fe1ee78de1d316ee027fea2ad5fe3c0d86f25a
• PRG1: 6ca47e9da206914730895e45fef4f7393e59772c1c80e9b9befc1a01d7ecf724

You can edit config.asm to change some build options; see that file for details.

Assembly

The "source" lives in the src directory:

• prg-x-x.asm are the program banks. They are grouped in pairs, as that is how SMB2 loads them. If you want to change this, you will need to split them apart again.
• defs.asm defines various enums and identifiers.
• ram.asm contains labels and definitions for RAM addresses.
• extras/ contains some additional fun things (see config.asm).
• levels/ contains level and enemy data.
• music/ contains music and sound data.
• This list is growing as we split the disassembly into smaller parts.

Contributing

• Fork the repository.
• Make changes.
• Submit a pull request!
• You are also encouraged to visit the Discord server if you have any questions.

See Also

• Data Crystal's SMB2 page
• CaptainSouthbird's SMB3 disassembly and Drakim's asm6f version
• Our Discord server