amiga-re-kit

Tools for reverse-engineering Commodore Amiga games from a disk image — extracted from three complete game projects (S.W.I.V., Turrican II, Superfrog) and made game-agnostic. One Python package (arek), one command line (arek), and an MCP server (arek-mcp) so an AI assistant can drive the same instruments you do.

The method is the point: first a complete, measured description of the original — only then anything else. Nothing here guesses. The decoder refuses instructions it does not model, the walker reports every indirect jump it cannot follow, the packers verify with the checksums the originals carry, and the emulator captures are compared byte for byte.

No game data is included or needed to run the kit. The tests use a hand-assembled 20-byte program and random buffers. Your disk image and Kickstart ROM stay on your machine, referenced from a git-ignored local.conf.

Install

pip install -e ".[mcp,dev]"         # or without extras: pip install -e .
python -m pytest                    # 1243 tests: synthetic data + CPU timings measured on Moira
arek --help

Optional: a patched headless vAmiga for anything that runs the original (arek shot, arek bpstate) — see docs/HEADLESS.md. Optional: m68k-elf-objdump for arek xref.

The workflow in commands

arek init myproject && cd myproject    # skeleton + local.conf (edit the paths)

# 1. measure the disk
arek adf info  disk.adf                # size, sha256, boot block, checksum
arek adf map   disk.adf                # entropy picture, one char per sector
arek adf regions disk.adf              # where code / data / packed blocks sit
arek scan      disk.adf                # packer signatures, verified Bytekiller blocks

# 2. unpack what the loader unpacks
arek adf track  disk.adf -n 1 -o trk1.bin
arek adf ls     disk.adf                              # AmigaDOS files, if the disk has a filesystem
arek adf cat    disk.adf -p LEVELS/L1 -o l1.atn       # one file, data blocks verified
arek pp20       file.pp -o file.bin    # PowerPacker 2.0
arek bytekiller trk1.bin --offset 0x200 -o main.bin
arek t2         INTR -o intr.bin       # Turrican II three-stage
arek atn        BLOCK -o out.bin --offset 0x1234   # Atomik (ATN!), block inside an image
arek hunk info  prog && arek hunk load prog --base 0x20000 -o h   # AmigaDOS executables
arek hunk split prog --chip prog2 --base 0xc00000 0x20000 -o h    # records split over two files

# 3. read the code - flow graph, not linear
arek dis    main.bin --base 0x20700 --walk 0x20700     # only reachable code
arek walk   main.bin --base 0x20700 --start 0x20700    # call tree + frontiers
arek walk   main.bin --base 0x20700 --start 0x20700 --inline 21800:until=8000  # data stored after bsr
arek hwscan main.bin --base 0x20700 --roots 0x20700    # the hardware boundary
arek copper ram.bin --base 0x0 --limit 200             # a copper list from a RAM dump
arek xref   prog.txt --syms syms.json                  # from an objdump listing
arek dis    main.bin --base 0x20700 --dcw              # linear, undecodable words as dc.w
arek dis    main.bin --base 0x20700 --walk 0x21234 --cycles   # 68000 clock count per instruction

# 4. translate and verify
arek recomp  main.bin --base 0x20700 --auto 0x21234 --main -o draw.c
arek recomp  main.bin --base 0x20700 --auto 0x21234 --timing \
             --jtab 21300:21400:12:4:bra --indirect 21350=21500,21600 --extern 21700=load_file -o game.c
arek bpstate --address 0x21234 --end 20 --out cap/before
arek bpstate --address 0x21300 --end 20 --out cap/after
arek diff    cap/before cap/after --range 0x60000 0x70000
arek shot    build/shots/title 5 10 --at 3 "joystick2 press 1"
arek trace   run build/l1.vtr --arm 196 --end 199 --break 0xc01106 --range 0:80000 c00000:80000
arek trace   show build/l1.vtr --field px=0xc0599e:h  # one row per hit, emulation never stopped
arek trace   run build/l1.vtr --arm 3 --end 60 --break 0xc01106 --inputs l1.txt --reglog regs.bin  # input per frame
arek selftest inputs                                   # is this VAHeadless frame exact? (synthetic disk)
arek --version                                         # version + decoder/recompiler hashes

Every command prints what it measured and nothing else. arek audit profile.json produces the JSON inventory + reachability record the method asks for (see examples/profile.example.json).

What is inside

Each module's docstring explains the format or the measurement it implements; docs/METHOD.md explains how they fit together.

MCP: let an assistant hold the instruments

pip install -e ".[mcp]"

Claude Code (.mcp.json in your project, or claude mcp add arek -- arek-mcp):

{"mcpServers": {"arek": {"command": "arek-mcp"}}}

The server exposes 22 tools (kit_info, adf_info, adf_map, adf_ls, adf_file, scan_packed, unpack, hunk_load, disassemble, walk, hwscan, recomp, xref, copper, headless_shot, headless_bpstate, trace_records, diff_captures, ram_at, …). kit_info returns the version and the SHA-256 of the decoder and recompiler; record it with every measurement. All of them take paths on the local machine; the server never fetches anything, never writes outside the paths it is given, and only returns measurements — the assistant sees entropy maps, listings and diffs, not your disk image.

A working session looks like: "map the disk" → "scan for packed blocks" → "unpack the block at 0x1f40 and walk it from its entry" → "which of these routines touch hardware?" → "recompile 0x21234 and compare its RAM writes with a capture of the original". Every answer is backed by a tool result.

Legal

The kit is MIT (see LICENSE). It ships no game data, no ROM, and no game-specific knowledge — the "engine without data" model: you supply the image you own. The vAmiga patches are modifications of MPL-2.0 sources and are published as required; see THIRD-PARTY.md.

Code comments inside the transplanted modules are partly in Czech (the projects' working language); public docstrings, the CLI and the docs are English.