Galaga '94 — native port

A native Windows and Linux port of Galaga '94 v2.1 (1994), the DOS shoot-'em-up by Arnold Pichler / APSS Austria. The game was released as MailWare: free to play and share, with a request to write to the author.

The port runs the original game code, not a remake. GALAGA.EXE (Turbo Pascal 6, 16-bit real mode) is statically recompiled to C: every x86 instruction becomes a line of C. That C runs on a small machine layer, and SDL2 stands in for the 1994 PC hardware:

1994 hardware	Port
VGA mode 13h / Mode X (planar, page flipping, 70 Hz retrace)	src/vga.c → SDL texture, 4:3, resizable, Alt+Enter for fullscreen
Keyboard interrupt (INT 9, port 60h scancodes)	SDL keys → XT scancodes; a game controller works alongside the keys
BIOS timer tick (INT 8 → INT 1Ch, 18.2 Hz)	real-time PIT
Sound Blaster through FX_SB.DRV (CT-VOICE)	.VOC decoding through SDL audio
PC speaker	square wave
DOS files	the data/ folder; high scores go to the user's save folder

Gameplay, speed and timing are the original's. The game paces itself on the 70 Hz VGA retrace, so it plays like it did on a fast 1994 PC.

Playing

Run galaga94 (galaga94.exe on Windows) next to the data/ folder. -f starts fullscreen.

	Keyboard	Controller
Move	← →	D-pad / left stick
Fire	Right Shift (also Space or Left Ctrl)	A / right trigger
Megabomb	Enter	B
Start / continue	↑	D-pad up
New game (title)	F1	Start
Difficulty (title)	F2	Y
Back to title	Esc	Back
Quit (title)	F10

High scores are saved to %APPDATA%\APSS\Galaga94\ on Windows and ~/.local/share/APSS/Galaga94/ on Linux.

Building

src/game.c is generated, and it's checked in so a build only needs a C compiler and SDL2.

• Windows: MSYS2 mingw32 gcc plus the SDL2 VC dev package. Run ./build.sh (set SDL= to the SDL2 folder; CONSOLE=1 gives a console build).
• Linux: sudo apt install libsdl2-dev, then ./build.sh.

To regenerate src/game.c from data/GALAGA.EXE (needs Python and capstone), run REGEN=1 ./build.sh.

Debug options:

• CFLAGS=-DTRACE logs every routine the first time it runs, plus frame rate, keys and sounds.
• GALAGA_INPUT="ms:scancode,..." and GALAGA_SHOT="ms:file.bmp,..." script keypresses and screenshots.
• GALAGA_QUIT_MS exits after a set time.

Layout

• tools/recomp.py: the recompiler. It descends from the entry point, every procedure prologue and the hand-written asm routines, then sweeps the gaps.
• tools/disasm.py: listing for reading the code (out/galaga.asm).
• src/cpu.h: registers, memory and 286 flag semantics.
• src/runtime.c: loader, run loop, interrupts, DOS/BIOS.
• src/vga.c, src/sound.c, src/platform.c: the devices and the SDL front end.
• data/: the game files, unchanged from reference-files/gal94_v2.zip except GALAGA.CFG, which is set to Sound Blaster sound. SETUP.EXE isn't needed.

Credits

Galaga '94 © 1994 Arnold Pichler, APSS Austria, distributed as MailWare. "Galaga" is a Namco trademark; this is the 1994 fan game, not Namco's.