What was done
kDylanHayes decompiled Mystery House from its 1987 public-domain release into assembler source that rebuilds the original files byte for byte, with every routine named and the game database decoded.
This project is a complete decompilation of Hi-Res Adventure #1: Mystery House by Ken and Roberta Williams (On-Line Systems, 1980). It starts from the 1987 public-domain release for the Apple II. Commits in the repository carry Claude co-author trailers.
How it was done
The result is assembler source that rebuilds the original files byte for byte. Every routine is named and documented, and the whole game database is decoded: rooms, objects, words, messages, rules and pictures. Standard ca65 assembler is used and the build needs only python3. A progress report measures the build routine by routine against the expected original programs. The one exception is DOS 3.3 on the built disk.
Results
A build script rebuilds everything and reports matching progress, with a check mode that fails unless all of it matches. A bugfix mode builds the same game with documented bugs fixed. A bootable disk image of the original or the bug-fixed game is published for any Apple II emulator. Tests include a tour of every room and every death, which run 347 of the game's 348 command rules and all its turn rules.