Zelda3

A reimplementation of Zelda 3.

About

This is a reverse engineered clone of Zelda 3 - A Link to the Past.

It's around 70-80kLOC of C code, and reimplements all parts of the original game. The game is playable from start to end.

You need a copy of the ROM to extract game resources (levels, images). Then once that's done, the ROM is no longer needed.

It uses the PPU and DSP implementation from LakeSnes. Additionally, it can be configured to also run the original machine code side by side. Then the RAM state is compared after each frame, to verify that the C implementation is correct.

I got much assistance from spannierism's Zelda 3 JP disassembly and the other ones that documented loads of function names and variables.

The game also supports enhanced aspect ratios of 16:9 or 16:10 (see ExtendedAspectRatio in zelda3.ini). It also supports MSU higher quality music soundtracks.

Dependencies

• the libsdl2-dev library
  • Windows: automatically installed with NuGet
  • Ubuntu: apt install libsdl2-dev
  • macOS: brew install sdl2
• a tables/zelda3.sfc US ROM file (for asset extraction step only)
  • SHA256 : 66871d66be19ad2c34c927d6b14cd8eb6fc3181965b6e517cb361f7316009cfb.
• The pillow and pyyaml python dependencies used by the assets extractor.
  • python -m pip install -r requirements.txt

Compiling

Look at the wiki at https://github.com/snesrev/zelda3/wiki for more help.

Windows

First extract and compile resources.

cd tables

Run python3 extract_resources.py to extract resources from the ROM into a more human readable format.

Run python3 compile_resources.py to produce .h files that get included by the C code.

Then build the .sln file with Visual Studio.

Linux/macOS

make

Advanced make usage ...

make -j$(nproc) # run on all core
make clean all  # clear gen+obj and rebuild
CC=clang make   # specify compiler

Usage and controls

The game supports snapshots. The joypad input history is also saved in the snapshot. It's thus possible to replay a playthrough in turbo mode to verify that the game behaves correctly.

The game is run with ./zelda3 and takes an optional path to the ROM-file, which will verify for each frame that the C code matches the original behavior.

Button	Key
Up	Up arrow
Down	Down arrow
Left	Left arrow
Right	Right arrow
Start	Enter
Select	Right shift
A	X
B	Z
X	S
Y	A
L	D
R	C

The keys can be reconfigured in zelda3.ini

Additionally, the following commands are available:

Key	Action
W	Fill health/magic
Shift+W	Fill rupees/bombs/arrows
Ctrl+E	Reset
P	Pause (with dim)
Shift+P	Pause (without dim)
Ctrl+Up	Increase window size
Ctrl+Down	Decrease window size
T	Toggle replay turbo
O	Set dungeon key to 1
K	Clear all input history from the joypad log
L	Stop replaying a shapshot
R	Toggle between fast and slow renderer
F	Display renderer performance
F1-F10	Load snapshot
Alt+Enter	Toggle Fullscreen
Shift+F1-F10	Save snapshot
Ctrl+F1-F10	Replay the snapshot
1-9	run a dungeons playthrough snapshots
Ctrl+1-9	run a dungeons playthrough in turbo mode

License

This project is licensed under the MIT license. See 'LICENSE.txt' for details.