havoc-remaster/docs/HANDOFF.md

Havoc Remaster - Session Handoff

Read this first. It is a self-contained bootstrap for continuing the Havoc reverse-engineering and remaster work in a fresh session (including on Linux). It assumes no prior conversation memory. Companion docs: docs/PATCHES.md, docs/FORMATS.md, docs/METHODOLOGY.md, docs/WEAPONS.md.

Last updated at the end of the session that got the game booting and cracked GRAFIX.

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1. What this project is

Reviving Havoc (Reality Bytes, Inc., 1995): a first-person, software-rendered 3D vehicular-combat shooter for Win95/98. The binaries are 32-bit PE (i386), DirectDraw + DirectSound, no Direct3D (the 3D is a software rasterizer). It is NOT DOS/16-bit, so DOSBox is the wrong tool.

End goal: port to Godot as a remaster with QoL (widescreen, higher-res, rebindable input, fixed-timestep physics). Three planned variants:

1. Faithful 1:1 (original bugs preserved as an option, including FPS-coupled cockpit physics).
2. Remaster (bug fixes, widescreen, rebindable input, higher-res).
3. Roguelite (procedural worlds, extra tanks) as a separate mode.

Two active work streams for the next sessions:

• A. Ghidra decompilation of HAVOC.EXE to recover game logic (weapons, AI, physics, cheats, the FPS-coupling, level/entity loaders).
• B. Asset cracking of the remaining WORLDS/ and .FF formats.

The user wants a detailed blog post of the whole RE process, so when you crack something, write down the discovery steps and dead ends, not just the final spec. Keep notes in docs/.

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2. Current state (what works / what is done)

• The game boots and is fully playable on Windows 11 via dgVoodoo2 (DirectDraw wrapper, windowed). Loads levels, enemies shoot, etc. This was the big unlock this session.
• NOCD + copy-protection fix: HAVOC_NOCD.EXE is the patched original (28 patches). The final blocker was a copy-protection check in the data-file loader 0x42a480 that only accepted files loaded from the CD drive; a 14-byte patch makes it accept the local files. Full write-up and patch table in docs/PATCHES.md.
• Formats cracked: .FF archives, MUSIC.FF (17 songs + FL Studio pack), INTRFACE.FF bitmaps, and now GRAFIX0N.DAT (64x64 texture tilesets, tools/grafix_extract.py). See docs/FORMATS.md.
• MAP layout partially decoded: MAP0101.MAP is a 2-byte-per-cell grid, ~192x144 (384-byte rows, found via row autocorrelation). Cell semantics (which byte is tile vs height) still TBD.
• Known open gameplay issue: movement/physics is FPS-coupled (one sim step per rendered frame, no fixed timestep). Workaround in place: dgVoodoo FPSLimit set to 30 (tunable). The user's memory says the in-game "minimal" HUD mode was NOT FPS-coupled while "cockpit" mode was, which suggests a limiter/delta path already exists in the binary for one mode. Finding that in Ghidra is a priority (see section 7).

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3. Environment (Windows -> Linux)

The repo lives on navi at /Library/Development/devl/Havoc (mounted on the Windows box as Z:\Development\devl\Havoc). On Linux you work directly in that path.

Tooling used this session and how it maps to Linux:

Purpose	Windows (this session)	Linux equivalent
Python	C:/Python313/python.exe	python3
Disassembly	radare2 + r2pipe (pip)	same: apt/pacman install radare2, pip install r2pipe
Image output	Pillow (pip install pillow)	same
Decompiler	(not yet used)	Ghidra (Java, cross-platform) - the main Linux task
Run the game	dgVoodoo2 on native Windows	Wine + dgVoodoo (test only; not needed for static work)

Windows-only tools that do NOT port (and are no longer needed): the crash diagnosis used WER minidumps from %LOCALAPPDATA%\CrashDumps parsed in pure Python, and a ctypes Win32 debugger (tools/dbg_path.py). Those were for the boot crash, which is solved. Decompilation and asset cracking are pure static analysis and run fine on Linux.

All the extraction tools (ff_extract.py, grafix_extract.py) are cross-platform Python (they use os.path, avoid Windows-isms).

Note: the game itself only runs on Windows (or Wine). Linux sessions are for Ghidra + asset extraction, which need only the files, not a running game.

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4. Repo, git, and constraints

• Remote: Forgejo, private repo git.opensourcesolarpunk.com/pyr0ball/havoc-remaster (personal pyr0ball account, not the CircuitForge org). Origin is already configured.
• Pushing: the user pushes on request. Token lives in a local .env.mirror file (outside the repo) as FORGEJO_TOKEN - never print it, never store it in .git/config. Push via git -c http.extraheader="Authorization: token $TOKEN" push for a one-time push.
• Commits: solo repo, history is on main. Commit style: conventional prefixes (feat:, docs:, chore:). Every commit message ends with the two trailer lines the harness provides (Co-Authored-By + Claude-Session).

Hard constraints (do not violate):

• Never commit original game data or binaries (copyright, Reality Bytes 1995): *.EXE *.DLL *.FF *.DAT *.MAP *.INI *.cue *.bin, BIGFILE.DAT, WORLDS/, tmp_cd/, the Ghidra install/project, and derived audio/art are all in .gitignore. When staging, use explicit paths (not git add -A) and sanity-check git diff --cached --name-only.
• No emdashes in any output (user style preference). Use plain hyphens.
• Document discovery process for the blog (see section 1).

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5. The binary: layout and key addresses

HAVOC_NOCD.EXE = patched HAVOC.EXE, 485,376 bytes, 32-bit PE i386, image base 0x400000, loads at preferred base (so runtime VAs == static VAs).

Section file-offset (FO) to virtual-address (VA):

Section	Raw FO	RVA	FO -> VA
.text	0x00400	0x01000	VA = FO + 0x400C00
.rdata	0x67000	0x79000	VA = FO + 0x412000
.data	0x69400	0x7C000	VA = FO + 0x412C00
.idata	0x6EC00	0x82000	VA = FO + 0x413400

Control-flow map (verified this session):

VA	What it is
0x464657	CRT entry point
0x407C90	WinMain. Allocs game object (vtable 0x4791A0), calls 0x434040 (init); on success calls vtable[7] = 0x43AC40 (main loop)
0x434040	Main init: allocates ~30 subsystem objects, loads title/GAMIMAGE, palette fade. Calls 0x418600. Returns AX=0 on success
0x418600	DirectDraw + archives + sound init. GRAFIX/world files load during this
0x43AC40	MAIN GAME LOOP (vtable[7]). State machine; state byte at [this+0x18]; loops while 0x10 <= state < 0xf0. Per-frame calls vtable[8]=0x436170, vtable[17]=0x43adc0 (msg pump), vtable[9]=0x4361d0. Exits when state = 0xf0. No frame limiter here = FPS-coupled
0x4791A0	Game object vtable (0x14-entry)
0x42a480	WORLDS\ data-file loader (the copy-protection function, now patched at FO 0x29a2b)
0x439380	Stream open method: CreateFileA([this+4], ...), vtable 0x479af8
0x444db0	GRAFIX0N.DAT loader (byte-swaps BE records; template for reading other WORLDS loaders)
0x40C8E0	Busy-wait frame limiter (~60/sec via timeGetTime), used in palette-fade / state transitions (0x40CAE0), NOT in the gameplay loop
0x40b5b0	Win32 WndProc dispatch (msg 2 WM_DESTROY -> 0x40b680 sets state=0xf0 + PostQuitMessage; focus msgs 7/0x1c handled)
0x409FC0	DirectSound init
0x42D970	show_error_dialog (patched to RET so failures do not popup)
0x4824E4	timeGetTime IAT; [0x47e56c] holds a 60Hz tick baseline (set once, not used as a per-frame delta)

Reproduce any disassembly with r2:

python3 -c "import r2pipe; r=r2pipe.open('HAVOC_NOCD.EXE',['-e','bin.relocs.apply=true']); print(r.cmd('pd 60 @ 0x43ac40'))"

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6. File formats: status

Cracked (see docs/FORMATS.md for specs and tools/ for extractors):

• .FF "FlashFile" archive (tools/ff_extract.py).
• MUSIC.FF: 97 WAV segments + 17 PLST-sequenced songs + FL Studio pack.
• INTRFACE.FF: bitmap system (BitB/BitR headers, XPAL palettes, STR# string tables).
• GRAFIX0N.DAT (tools/grafix_extract.py): BE header (size@0x08, count@0x0c), 16-byte entry records (BE offset + id), per-graphic blocks (BE w/h/frames/id + 8-bit indexed pixels). 64x64.

TODO (the asset-cracking stream):

• MAP.MAP: 2-byte-per-cell grid, ~192x144 confirmed. Next: disassemble its loader to get exact dims + which byte is tile vs height. Find the loader by searching for the code that opens "MAP" filenames (same pattern as GRAFIX via 0x42a480).
• STUF.DAT: entity placement. Contains ASCII "Item" records - very parseable. Start here for a quick win.
• LAND.DAT: terrain geometry (hardest). BE fields; music-track id is a BE u16 at offset 0x12 (per prior notes). Has 4-byte records around 0x20 (17 70 00 c0 ...).
• OBJECTS.FF: 3D models (vehicles, enemies, pickups) - not yet touched.
• World palette: GRAFIX tiles currently render with a UI XPAL palette. The true per-world 3D palette is TBD - likely loaded during 0x418600 init or embedded per-world. Finding it makes all extracted art color-correct.

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7. Ghidra decompilation stream (primary Linux task)

Load HAVOC.EXE (or HAVOC_NOCD.EXE) into Ghidra (x86 32-bit, image base 0x400000). Import the key addresses from section 5 as labels to bootstrap. High-value targets, roughly in order:

1. The FPS-coupling / render modes. The user reports cockpit mode is FPS-coupled but the minimal HUD mode is not. Find the mode toggle and the two render/update paths. Determine whether minimal mode uses a frame limiter (Sleep/timeGetTime) or a fixed-timestep/delta update. That path is the template for the remaster's fixed-timestep, and possibly a cleaner in-binary fix than the dgVoodoo FPS cap. Start from the main loop 0x43AC40 and its per-frame methods 0x436170 / 0x4361d0, and the busy-wait limiter 0x40C8E0.
2. Cheat code handler. Codes mmm (max heatseeker), vvv (free vehicle), sss (shield), hhh (health), aaa (ammo). Find the keyboard-buffer matcher; it will reveal the full cheat list and the player/inventory structs.
3. Weapon system. 6 primary classes (Laser, Disc, Shockwave, Fireball, Plasma, VARG) infinite ammo; 14 secondary lines (see docs/WEAPONS.md, from string tables STR#7D02/7D03). Recover the weapon data tables, upgrade tiers, and firing logic.
4. Player / vehicle physics (movement constants, the FPS-coupled step) and enemy AI.
5. Level + entity loaders (MAP/LAND/STUF) - decompiling these also directly finishes the asset-cracking stream (get exact record layouts instead of guessing).
6. World table: 6 worlds stored in reverse (Overlord, Wasteland, Malterra, Tyrak, Fallout, Badlands), 3 levels + boss + bonus each. See docs/FORMATS.md and game-mechanics notes.

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8. Methodology playbook (how the cracking was done)

• Crack a format via its loader, not guesswork. Find where the game opens the file (filenames are in .data; the loader 0x42a480 builds WORLDS\<name> paths), then read the loader's parse code. GRAFIX was solved by reading 0x444db0 (the 16-byte record stride and BE->LE byte-swap gave the record layout exactly).
• These WORLDS files are big-endian (Mac-origin data; the loaders byte-swap). Always try BE first for headers/records.
• Find grid dimensions by row autocorrelation (minimize mean abs diff between byte j and j+stride over candidate strides); then render grayscale at that width and eyeball for coherent structure. That is how MAP's 384-byte row (192x2) was found.
• Verify visually. Render extracted pixel data to PNG and build contact sheets; correct decodes look like real art. Pillow Image.frombytes('P', (w,h), data); putpalette(...).
• r2pipe pattern for scanning: open with bin.relocs.apply=true, iterate .text FOs looking for opcode patterns (e.g. ff 15 CALL [IAT], a1/8b 05 mem reads) and convert FO->VA.

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9. Tool inventory (tools/)

• ff_extract.py - .FF archive extractor (archives, songs, FL pack). --help for flags.
• grafix_extract.py - GRAFIX0N.DAT -> PNG (-p <768-byte palette>).
• dbg_path.py - Windows-only ctypes debugger (used for the boot crash; keep for reference).
• Many r2*.py / find_*.py / analyze*.py - one-off RE probes from the crash hunt and format work. Useful as r2pipe examples; not all are load-bearing.
• run_probe.bat / run_and_log.bat - Windows launch helpers (repro/testing on Windows only).

Palettes: extract with python3 tools/ff_extract.py INTRFACE.FF -o tools/out_intrface, palettes land in tools/out_intrface/raw/XPAL*.DAT (768-byte RGB).

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10. Immediate next steps (suggested)

1. (Asset, quick win) Crack STUF<lvl>.DAT entity records (ASCII "Item" markers).
2. (Asset) Disassemble the MAP loader to lock MAP dims + cell meaning; render a proper level map.
3. (Ghidra) Stand up the project, label the section-5 addresses, and chase the render-mode / FPS-coupling path (item 7.1) - it informs both the exe fix and the Godot physics.
4. (Remaster) Once STUF + MAP + a world palette are done, there is enough to scaffold the Godot project (empty today) and load a real level.

The FPS workaround (dgVoodoo FPSLimit = 30) is a stopgap; the user is tuning the value. A proper fix is either a frame limiter patched into 0x43AC40 (the game imports Sleep) or, better, adopting the minimal-mode timing path once Ghidra reveals it.