Case study

ReC98: the Touhou PC-98 Restoration Project

Reconstructs C++ and assembly source for the first five Touhou games, released by ZUN for the NEC PC-9801 in 1997–1998, under a rule that no master commit may change the decompressed program image or relocations of any original executable as compared by the project’s mzdiff tool. TH01 was fully decompiled in August 2022; code not yet decompiled stays in the tree as IDA-generated disassembly, and the project’s blog documents what each part of ZUN’s code does. Separate debloated and anniversary branches restructure the code and fix bugs as bases for ports and mods.

Targets: Game
Category: Independent reconstruction cases
Relationship: Independent reconstruction project
Sources reviewed: 2026-10-19
Evidence class: C2 code & docs, no demo or download

Stars: 886
Last commit: 2026-03-16
Language: Assembly

GitHub data as of 2026-11-10

Copy as Markdown View JSON Cite

Evidence

Observed: Code, documentation and a download method observed; no demo found.
Checked: 2026-11-09

How evidence classes are assigned

Requirements & limits

The project targets the first five Touhou PC-98 games. TH01 was fully decompiled in August 2022; other games remain in progress. Master permits only instruction-encoding differences and trailing zero padding under mzdiff; ports use the debloated branch and bug fixes use anniversary or single-fix branches.
Running the built PC-98 executables requires each game’s original files beside the output. The repository omits original asset data. Builds require Borland Turbo C++ 4.0J and Borland Turbo Assembler 5.0 or later (TASM32.EXE); neither is bundled.
Windows 11 x64 and Windows XP 32-bit are tier-1 build platforms; Wine on 64-bit x86 Unix is tier 2. The output runs in DOSBox-X or the project’s Neko Project II debug fork.
The root has no license file. Bundled MS-DOS Player and Tup builds are GPLv2; master.lib, the Pi loader, SPRITE16 and KAJA PMD files are third-party components. Rights to the original games remain with their owner.

Cite

BibTeX

@misc{rec98-touhou-pc98-restoration-case,
  title = {{ReC98: the Touhou PC-98 Restoration Project}},
  howpublished = {\url{https://github.com/nmlgc/ReC98}},
  url = {https://github.com/nmlgc/ReC98},
  urldate = {2026-10-19},
  note = {Awesome REA entry: \url{https://awesomerea.org/resources/rec98-touhou-pc98-restoration-case/}}
}

Plain text

ReC98: the Touhou PC-98 Restoration Project. https://github.com/nmlgc/ReC98 (accessed 2026-10-19). Awesome REA entry: https://awesomerea.org/resources/rec98-touhou-pc98-restoration-case/

Useful? Star Awesome REA on GitHub2.4k

About this entry

The description was reviewed against primary sources.

Report an outdated entry Suggest a translation fix

Primary sources

README.md GitHub · nmlgc/ReC98 · Revision b6ba5b0
CONTRIBUTING.md GitHub · nmlgc/ReC98 · Revision b6ba5b0
bin/README.md GitHub · nmlgc/ReC98 · Revision b6ba5b0
build.bat GitHub · nmlgc/ReC98 · Revision b6ba5b0
Tupfile.lua GitHub · nmlgc/ReC98 · Revision b6ba5b0
https://github.com/nmlgc/ReC98/tree/28d59d31331e27fcbe61d1b65bd8c0cd618757d8
https://github.com/nmlgc/ReC98/tree/c7019963ac643333114ccba9ef10adb3728f2384
https://rec98.nmlgc.net/