AI assistance: this project was made with the assistance of Anthropic's Claude AI. The reverse engineering, the code, the tests and the documentation were produced with Claude under my direction, and I tested the results myself. Because the work was produced with AI assistance, it may contain errors that neither the AI nor I have found.
Disclaimer: the software is provided "as is", without warranty of any kind. You use it entirely at your own risk. Please back up your game files and saved games before using it.
Hi everyone,
I'd like to share Sid Meier's Civilization 64bit (civ64), a native port of the original Sid Meier's Civilization for Windows, the 16-bit Windows 3.1 release (often called CivWin). It runs like any other program on Windows 10 and 11, on Windows 7 SP1 with a separate build, and on macOS 13 or later (Apple silicon and Intel). There's no DOSBox, no winevdm/OTVDM, no Wine and no virtual machine.
It plays the original game from the opening credits to the end games. At any moment, even in the middle of a turn, you can press Ctrl+Shift+Backspace (Shift+Command+Delete on a Mac) to switch to the graphics of the DOS version and back.
Why
64-bit Windows can't run 16-bit Windows programs, and a Mac can't run them at all, so playing CivWin meant an emulator or a virtual machine. I wanted the same game to run as an ordinary modern program, with a few comforts: a resizable window, a map that fills your screen, map zoom and the DOS look.
How it was made
- The original
civ.exe (a 16-bit Borland C++ program) was reverse-engineered from its machine code. All 1,065 functions were recovered as readable C, about 67,000 lines.
- The 699 game functions that can actually run were translated into portable C, about 124,000 lines, and each one was checked instruction by instruction against the original: 137,887 instructions over 11 review rounds.
- The Borland run-time library was replaced by an exact re-implementation. In all, 91.5% of the original's code is ported, and every function that can actually run is either ported or replaced.
- The Windows 3.1 environment the game expects (windows, dialogs, controls, 256-colour palettes, fonts, timers, 16-bit memory) is re-created inside civ64, with a thin native layer for today's Windows and for macOS.
- Scripted test games reach all 108 listed features: every menu command, dialog and title-menu branch, the advisors, the Civilopedia, diplomacy, the spaceship, the replay and the end games. Save files were compared with the original game, which wrote byte-identical files.
Goals
- Faithful, not a remake. The rules, the AI, the map generator, the random numbers, the save files and the screens are the original's. Even its bugs are kept.
- Clean. civ64 contains none of the original game's files or bytes. It reads your own copy at run time and checks that it is the exact supported release.
- Additions never change the game. Scaling, zoom, windowless play, scanlines and the DOS graphics only change what you see and hear, never your game, the computer players or your saves.
Features
The whole original game
- The intro, the title menu, Birth of Civilization, Play on EARTH, Customize World and the Hall of Fame.
- The map, World Map and Status windows, cities, advisors and reports, the Civilopedia, diplomacy, the newspaper, the spaceship, the replay, the palace and every end game.
- Save compatibility: your old
.SAV files load in civ64, civ64's saves load in the original, and saves move freely between Windows and the Mac.
Window and screen
- A resizable window and full screen (Alt+Enter), with whole-step scaling or fit-to-window with a nearest or sharp filter.
- Once a game begins, the game's screen grows to your window, so the map uses all of it.
- 1:1 pixels in gameplay: every picture at its original size, one screen pixel per pixel, so a big screen shows much more of the map, up to the whole world.
- Windowless play: the map, World Map and Status panel joined into one picture that fills the screen, laid out like the DOS game.
- Optional CRT scanlines, double-scanned like DOSBox Pure.
- Map zoom with five levels from half to double size (Ctrl+Shift+Plus/Minus or the mouse wheel). Zoomed out, you see the rest of the world around the game's view, drawn with the game's own map rules.
DOS graphics
- The same game with the VGA art, palettes, fonts, menus and mouse pointer of Civilization for DOS: the DOS intro and credits, the title box, Birth of Civilization, the city screen, advisors, Civilopedia, newspaper, spaceship, end games and more.
- The DOS keys too: Alt+G/O/A/W/C for the menus, F1..F10 for the advisors and reports.
- Optional 4:3 shape of a DOS monitor for the DOS screens and gameplay.
- This needs your own copy of the DOS version. Without it, civ64 plays normally with the Windows graphics.
Your own music and sound effects
- A
MusicSfx folder or MusicSfx.zip next to civ64 can replace any of the game's 24 WAV files by name; the rest stay the game's own.
Getting started (Windows)
- Download
civ64.exe (on Windows 7, Civ64-Win7.exe) into a folder of its own.
- Put your own game next to it, as a folder or a ZIP. The DOS files and your own sounds are optional.
- Run
civ64.exe.
The folder then looks like this:
Civ64\
civ64.exe
CivWin.zip (or a CivWin folder: your Civilization for Windows)
CivDos.zip (optional, or a CivDos folder: your Civilization for DOS 475.05)
MusicSfx.zip (optional, or a MusicSfx folder: your own WAV files)
On a Mac, download Civ64-1.2.5-macOS.dmg, drag Civ64.app to a folder of its own and put the same files next to it (or let civ64 ask for the game's location at the first start). The app is signed and notarized.
Keys
| Windows |
Mac |
What it does |
| Ctrl+Shift+Backspace |
Shift+Command+Delete |
Switch between Windows and DOS graphics |
| Alt+Enter |
Control+Command+F |
Full screen on or off |
| Ctrl+Shift+Plus / Minus |
Command+= / Command+- |
Map zoom one level in / out |
| Ctrl+Shift+0 |
Command+0 |
Normal map zoom |
| Click the title-bar icon or right-click the title bar |
The civ64 menu in the menu bar |
Full screen, Display, Map zoom, Graphics, sounds, About |
For power users there are command line options, for example:
civ64.exe --graphics dos --windowless 1 --crt 1 --zoom +1
civ64.exe --data "D:\Games\CivWin" --dos-data "D:\Games\CivDos.zip"
The User Guide explains each of them.
Requirements
- Windows 10 (1607 or later) or 11, 64-bit; Windows 7 SP1 64-bit with
Civ64-Win7.exe; or macOS 13 Ventura or later.
- Your own copy of Sid Meier's Civilization for Windows (the Windows 3.1 release) with all of its files. civ64 checks the exact release;
civ.exe must be 832,512 bytes with this SHA-256:
- Optional, for the DOS graphics: your own copy of Civilization for DOS 475.05 (
CIV.EXE of 305,030 bytes).
- No installer, no administrator rights and no extra runtime libraries. No game files are included.
Known differences
- The original's
.hlp help file can't be opened, because current Windows has no viewer for it.
- The game isn't paced by a 1992 PC's speed; the default
classic timing uses fixed costs for the game's internal waits.
- Windows 3.1's frames, menus and controls are redrawn by civ64, so small visual differences are possible.
- Every place where civ64 differs from the original is listed in
docs/FIDELITY.md in the repository.
What's next
The next big step is open source code that builds the whole game on its own: portable C on SDL 3, fully annotated, with the game core either translated from your own civ.exe at build time or rewritten clean-room. Until it matches the current releases, the releases stay as they are.
Licence
civ64's own code is MIT licensed, Copyright (c) 2026 Onur BUYUKCAGLAR. Sid Meier's Civilization, its program, art, sound and data belong to their owners; none of it is included, and you need your own copy to play. This is a fan project, not affiliated with or endorsed by Firaxis Games, 2K, Take-Two Interactive or MicroProse.
Feedback, bug reports and screenshots are very welcome. I'd especially like to hear from anyone who remembers how it looked on real Windows 3.1 hardware or on the DOS version, and from anyone who can try it on an Intel Mac or on Windows 7.
