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Rebuilding a 1991 Windows Strategy Game from Assembly — Second Conflict in Python

Second Conflict is a 1991 turn-based space strategy game for Windows 3.x, written in Borland C++ by Jerry W. Galloway. Up to ten factions compete to conquer a galaxy of 26 star systems, dispatching fleets, managing planetary production, and grinding through attritional ship-to-ship combat. The executable — SCW.EXE — is a 16-bit Windows NE binary that has never had its source released. This post documents how we reverse-engineered the game's file formats, mechanics, and UI from scratch, then rebuilt the whole thing in Python and pygame.

6,034
lines of Python
538
decompiled functions
26
star systems
15+
dialog screens

1. Starting Point — Why Ghidra?

The project began with a single goal: faithfully preserve the game's mechanics, not just make something inspired by it. That means reading the actual binary. Ghidra, the NSA's open-source reverse-engineering framework, handles 16-bit NE executables well enough to produce readable pseudo-C for most functions. We exported the full decompilation — 25,826 lines across 538 functions — into decomp_scw.txt and used it as the authoritative reference throughout.

The core workflow was: find a dialog or behavior in the running game, locate the corresponding Windows message handler in the decompilation (Ghidra labels them FUN_XXXX_YYYY), read the pseudo-C, and translate that logic into Python. Where the decompiler output was ambiguous we went back to the raw hex.

The original's dialog box identifiers (e.g. COMBATPAUSEDLG, REINFVIEWDLG) were recoverable from the NE resource table strings, which gave us reliable anchor points to search the decompilation.

2. Decoding the Save-File Format

Before writing any game logic we had to be able to read and write the original .SCN/.SAV save files. The loader function (FUN_1070_013f) reads ten sequential sections:

SectionSize (bytes)Contents
Header18Star count, sim-steps per turn, version 0x0300
Stars99 × 26 = 2,574Star records with TLV garrison entries
Fleets in transit21 × 400 = 8,400Fleet records; 0xFF = free slot
Playersvariable9-byte name + 27 × uint16 attributes
Event logvariablePast-turn event strings
Misc state sections

Several false starts happened here. The player record layout was initially read backwards — attributes came before the name in our first pass, not after. Star 0 turned out to use different field offsets than stars 1–25 (its coordinates are at bytes 9–10 rather than 1–2). These were caught by diffing known scenario files against parsed output until every field matched.

TLV garrison encoding

Each star's garrison (the ships defending it) is stored as a sequence of 7-byte Type-Length-Value records. Each entry encodes a faction ID, ship type, and count. The parser walks these until it hits a terminator byte, building a list of GarrisonEntry objects that the engine then queries by ship type.

# From scenario_parser.py — reading one garrison entry
ship_type  = data[off]
faction_id = data[off + 1]
ship_count = struct.unpack_from('

3. Extracting Original Bitmaps from the NE Executable

The game's artwork lives inside SCW.EXE and SCWTIT.DLL as NE resources. The complication: Windows NE DIB resources are stored without the 14-byte BITMAPFILEHEADER that modern tools expect. We wrote a parser in assets.py that walks the NE resource table directly:

  1. Read the NE header offset from the MZ stub at byte 0x3c.
  2. Follow the resource table pointer inside the NE header.
  3. Find entries of type 0x8002 (RT_BITMAP).
  4. Apply the alignment shift from the resource table header to get the true file offset and length.
  5. Prepend a synthesised BITMAPFILEHEADER (calculating the pixel-data offset as 14 + hdr_size + palette_entries × 4).
  6. Load the result via pygame.image.load(io.BytesIO(header + dib_data)).

Star sprites are stored as white-on-black 15×15 bitmaps, which made tinting trivial: pygame.BLEND_RGB_MULT multiplies each pixel by the player's faction colour, turning white into any desired hue. The title screen art (288×360) is pulled from SCWTIT.DLL and shown in the About dialog when the DLL is present; the dialog degrades gracefully to text-only otherwise.

# assets.py — tinting a white sprite to player colour
surf = base_sprite.copy()
tint = pygame.Surface(surf.get_size())
tint.fill(player_colour)
surf.blit(tint, (0, 0), special_flags=pygame.BLEND_RGB_MULT)
return surf

4. Game Engine

The engine lives under second_conflict/engine/ and is deliberately stateless — every function takes the GameState dataclass and mutates it in place, matching the original's single shared-memory model.

engine/
  turn_runner.py  — orchestrates one full turn
  combat.py      — warship attrition & combat records
  production.py  — per-planet ship production
  fleet_transit.py— dispatch & advance fleets
  revolt.py      — loyalty decay & planet revolts
  events.py     — human-readable event log
  distance.py   — star-to-star travel time

Combat

The original game resolves combat as multiple rounds of attrition between the attacking warships (any fleet arriving at an enemy star) and the defending warships (always the star's current owner's garrison). Each round a random fraction of each side is destroyed — the exact formula derived from the decompiled _attrition function.

Combat produces a CombatRecord dataclass — attacker/defender factions, initial and final ship counts, a list of per-round (atk_hit, def_hit) tuples, and the winning faction. turn_runner.py returns these records alongside the event log so the UI can animate them.

Bug we fixed Early on, the code picked the faction with the most warships as the defender, which flipped attacker and defender when the star owner had fewer ships than the attacker. The fix was simple: the defender is always star.owner_faction_id, mirroring what the original does.

Ship types

The original game has seven ship types. One caused confusion during RE: planet type 'S' in the scenario file was initially labelled "Scout" in our model. Cross-referencing the production dialog switch-case (offset +0x55 in the star record) with the scout-launch code revealed that offset stores StealthShip counts — so planet type S produces StealthShips, not scouts. Probe ships fill the scout role.

IDNamePlanet type
1WarShipW
2StealthShipS
3TransportT
4MissileM
5ScoutC
6Troopship
7ProbeP

5. The UI — Translating Windows Dialogs to pygame

The original game is a classic Windows 3.x dialog-heavy application. Every interaction — viewing your planets, dispatching a fleet, reading combat results — happens in a modal dialog box. We translated each WNDPROC into a Python class inheriting from BaseDialog, which handles the common pattern of: draw a bordered panel, render text rows, handle mouse hover/click on buttons, close with a return value.

Original IDPython classPurpose
ADMVIEWDLGAdminViewDialogAll owned planets with ship counts
SCOUTVIEWDLGScoutViewDialogIntelligence on enemy/neutral systems
REINFVIEWDLGReinfViewDialogIncoming friendly fleets
REVOLTVIEWDLGRevoltViewDialogPlanets at revolt risk
COMBATPAUSEDLGCombatPauseDialogContinue / Skip All between rounds
COMBATWNDPROCCombatAnimationAnimated per-round battle replay
FLEETVIEWDLGFleetViewDialogAll fleets in transit
PRODLIMITDLGProdLimitDialogSet production per planet type
UNRESTVIEWDLGUnrestDialogLoyalty across all factions

Combat animation

CombatAnimation is the most complex dialog. It replays a full CombatRecord visually: ship dots (using extracted sprites, tinted to each faction's colour) are scattered across a split battle area, and each combat round plays out as a phase sequence:

def _build_phases(self):
    phases = [('scatter', 600)]          # ships fly to positions
    for r in range(len(self.record.rounds)):
        phases += [
            (f'r{r}_red',    500),       # casualties highlighted red
            (f'r{r}_yellow', 350),       # dying ships turn yellow
            (f'r{r}_clear',  300),       # dead ships removed
        ]
    phases.append(('result', 0))         # outcome — wait for click
    return phases

Dots are drawn as alive (tinted sprite), dying (yellow rect), or simply absent. The state machine advances automatically on a timer, pausing at 'result' until the player clicks.

6. AI Players

Two AI layers exist. The Empire AI controls the neutral Empire faction — a standing enemy that pressures all players throughout the game. The Player AI handles CPU-controlled player factions in single-player games, making fleet dispatch and production decisions each turn based on heuristics derived from the original's behaviour.

7. Project Structure

second_conflict/
  model/    — GameState, Star, Fleet, Player dataclasses
  engine/   — pure game logic (no pygame)
  io/      — scenario_parser: read/write .SCN files
  ui/
    dialogs/ — 15+ modal dialog classes
    map_view.py   — interactive star map
    side_panel.py — right-hand fleet/turn panel
    sys_info_panel.py— selected star details
  ai/     — empire_ai.py, player_ai.py
  assets.py    — NE resource parser, sprite cache
main.py        — entry point, menu bar, event loop

The model and engine layers have no pygame dependency at all, which kept testing straightforward and would allow a headless server mode.

8. Lessons Learned

  • Trust the binary, not assumptions. Several fields were initially wrong because we assumed typical game layouts. The decompilation always won arguments.
  • NE resources are not PE resources. The 16-bit Windows NE format predates the PE format and has a completely different resource table structure. DIB bitmaps stored inside it lack the file header that modern tools expect — synthesising it from the DIB's own info header is the only way to load them.
  • White sprites are a tinting gift. If the original artist drew ship and star sprites in white-on-black, BLEND_RGB_MULT gives you faction colouring for free. No palette hacks required.
  • Stateless engine functions pay off. Keeping all game logic as pure functions over a serialisable state dataclass made save/load trivial and prevented entire classes of bugs where UI and model drifted out of sync.
  • Name things from the source. Using the original dialog IDs (ADMVIEWDLG, REINFVIEWDLG, etc.) as class-level docstring references meant that whenever something looked wrong, there was an unambiguous pointer back to the relevant decompiled function.

What's Next

The remaining work is mostly filling in edges: fog-of-war is not yet implemented (currently all stars are visible to all players), the diplomacy system is stubbed out, and a few of the original's more obscure mechanics — missile fleet speed bonuses, troopship boarding combat — are approximated rather than exact. The save-file round-trip is complete, which means existing original scenario files load and play correctly.

Note on legality Second Conflict is abandonware — the original publisher is long gone and the game is freely distributed on abandonware sites. The Python reimplementation does not distribute any original game assets; if SCW.EXE is present on the user's machine the engine will extract and use the original sprites, otherwise it falls back to procedural graphics.
second conflict in python Source Code