Icarus: Sanctuary of the Gods

Icarus: Sanctuary of the Gods (Droiyan), static recompilation

Recomp by Second Save

A native port of the 1998 Windows 95 RPG Icarus: Sanctuary of the Gods (Korean title Droiyan, KRG Soft / JC Research) for macOS, Linux and Windows. The game's x86 code (ICARUS.EXE, MSVC 5) is translated to C ahead of time, and a small runtime replaces the Win32 / DirectX 5 APIs it used with SDL3.

Nothing is emulated at run time: no Windows, no Wine, no CPU interpreter.

How it works

Piece	What it does
tools/recomp.py	Disassembles ICARUS.EXE (Capstone), finds every function (call targets, relocation table, incremental-link thunks, switch tables) and writes one C function per guest function into gen/.
runtime/rt.h, rt_core.c	CPU state, lazy flags, x87, string ops, dispatcher for indirect calls, host-to-guest callbacks.
runtime/w32_kernel.c	Imports and COM vtables point at "magic" addresses served by host functions. Also the guest heap, files (case-insensitive, copy-on-write saves) and process queries.
runtime/w32_user.c	Window, message queue, keyboard/mouse (SDL3), GDI text, wsprintf.
runtime/w32_ddraw.c	DirectDraw surfaces in guest memory (8- and 16-bit modes), Blt/BltFast/Flip, palettes, presentation.
runtime/w32_dsound.c	DirectSound buffers mixed in software, plus the CD audio music tracks.
runtime/w32_mm.c	Multimedia timers (delivered on the game thread), MCI cdaudio, the mmio RIFF reader.
runtime/w32_avi.c	AVIFile stream reading and a Cinepak decoder for the game's own movie player.
runtime/launcher.c, runtime/installer.c	Launcher window and the disc installer (ISO9660, InstallShield 3 via runtime/is3.h, CD audio, EXE check, memory image).
runtime/qol.c	Hardware cursor from the game's sprites, dialogue speed.
runtime/text.c	Replacement text renderer: anti-aliased, proportional Crimson Pro glyphs blended through the game palette (ICARUS_FONT=original for the 1998 font).
tools/prepare_data.py, tools/is3unpack.c	Rebuild the installed game from the original discs: ISO9660 extraction, the InstallShield 3 .Z archives (PKWARE DCL), and the CD audio tracks.

You need

• The two original discs as BIN/CUE images (ICAR_CD1.cue/.bin, ICAR_CD2.cue/.bin).
• A C compiler (clang or gcc; MinGW-w64 on Windows) and SDL3 (brew install sdl3, apt install libsdl3-dev, MSYS2 mingw-w64-x86_64-SDL3).
• Python 3 with capstone and pefile to regenerate gen/ (pip install capstone pefile).

Launcher

Running icarus opens the launcher:

• Game discs: pick disc 1 and disc 2 (.cue + .bin, a bare .bin, or .iso), then Install. The game files are unpacked from the original installer archives, ICARUS.EXE is checked against the release this build was made from, and the CD music is saved. This takes a few seconds; disc 2 must be a .cue for the music. Disc images are only read.
• Settings: window size, fullscreen, scaling, frame rate, mouse cursor, dialogue speed and font, sound, and whether to show the launcher at startup. Left-click a setting for the next value, right-click for the previous one.
• Play (or Enter) starts the game; Esc quits. icarus --play skips the launcher.

Data, saves and settings are stored per user: ~/Library/Application Support/Second Save/Icarus (macOS), %APPDATA%\Second Save\Icarus (Windows), ~/.local/share/Second Save/Icarus (Linux). When the working folder has a data/ folder (developer layout, see below), data/, save/ and icarus.cfg there are used instead.

Build

make build/is3unpack
make data CD1=path/to/ICAR_CD1.cue CD2=path/to/ICAR_CD2.cue   # builds data/ (about 870 MB, 530 MB of it CD music)
make gen PY=python3                                            # translate data/ICARUS.EXE -> gen/
make -j8                                                       # -> ./icarus
./icarus

data/ holds the installed game files, droiyan.ini (the CD drive the game reads from: D:\), and data/cd/ (the run-time CD contents: maps, movies, music as WAV). Saved games and options go to save/. The original files in data/ are never modified.

Controls

The game's own controls: mouse for everything, Space or click to skip the intro movie, Esc to skip the prologue. Added by this port:

Key	Action
Hold Tab	Fast-forward (4x)
F11 or Alt+Enter	Toggle fullscreen
F12	Screenshot to screenshots/
Click or any key during the boot logos	Skip straight to the title screen

Quality of life

• Lag-free mouse: the game's own cursor sprite is shown as the system cursor at the window's scale, so it moves at full display rate instead of one frame behind (HWCURSOR = 0 to disable).
• Display-synced frame rate: like on 1998 hardware, where Flip waited for the monitor, the game runs in step with the display: 60/75/85 Hz every refresh, 120/144 Hz every second one. No judder from a 60 fps game on a 75 Hz screen. FPS = 60 forces a rate.
• Sharp scaling: crisp pixels of even size at any window size or in fullscreen (integer upscale, then a smooth resize). SCALE_MODE = nearest | smooth | integer.
• Faster dialogue: text types twice as fast (TEXT_SPEED = 1 original, 0 instant).
• Readable font: anti-aliased Crimson Pro instead of the 1998 bitmap font (FONT = original).
• Lower sound latency, music that loops, and sound effects that load reliably.

Settings live in icarus.cfg (created on first run, next to where you start the game). Every KEY = value there is the same as setting the environment variable ICARUS_KEY.

Environment variables

Variable	Effect
ICARUS_DATA=dir	Game data folder (default ./data, or data/ next to the binary).
ICARUS_SAVE=dir	Save folder (default ./save).
ICARUS_SCALE=n	Initial window scale (default 2). ICARUS_FULLSCREEN=1 starts fullscreen.
ICARUS_SMOOTH=1	Bilinear scaling instead of sharp pixels.
ICARUS_MUTE=1	No sound.
ICARUS_WARP=1	Let the game move the host mouse pointer (SetCursorPos).
ICARUS_VERBOSE=1	Log files, surfaces, sound buffers and MCI calls.
ICARUS_TRACE=1	Log every Win32/COM call (ICARUS_TRACE_QUIET=Name1,Name2 hides noisy ones).
ICARUS_HEADLESS=1	No window (testing). With ICARUS_SHOT=file%04d.ppm and ICARUS_SHOT_EVERY=n it saves frames.
ICARUS_FONT=original	Use the game's original 8x16 bitmap font instead of the anti-aliased replacement.
ICARUS_AUDIO_DUMP=file.raw	Also write the mixed audio (s16 stereo 44.1 kHz) to a file.
ICARUS_FPS=n	Fixed frame rate instead of following the display refresh.
ICARUS_SCALE_MODE=m	sharp (default), nearest, smooth or integer.
ICARUS_TEXT_SPEED=n	Dialogue speed: 1 original, 2 default, 0 instant.
ICARUS_HWCURSOR=0	Draw the cursor in the game frame instead of as the system cursor.
ICARUS_VSYNC=0	No vsync; host pacing at 60 fps.
ICARUS_RECORD=f.rgb	Record raw 640x480 RGB frames at a constant ICARUS_RECORD_FPS (default 30), for trailers (tools/make_trailer.py).
ICARUS_STATS=1	Print presents/flips per second and the worst frame gap.
ICARUS_CONFIG=file	Settings file (default: per-user folder, or icarus.cfg in the developer layout).
ICARUS_LAUNCHER=0	Do not show the launcher (same as LAUNCHER = 0 in the settings).
ICARUS_LAUNCHER_SHOT=f.bmp, ICARUS_LAUNCHER_AUTO=play|install|quit	Testing: capture the launcher, then act.
ICARUS_KEYS=t:vk,..., ICARUS_CLICKS=t:x:y[:right],...	Scripted input at t seconds (testing).

| ICARUS_SNDTEST=slot:entry,... | Testing: 20 s in, load and play DROYSND.SNF entries through the game's own loader. | | ICARUS_CDDA_MAXSEC=n | Testing: cut every CD track to n seconds (checks music looping). |

tools/run_headless.sh SECONDS and tools/shots.sh T... wrap the testing knobs. Test runs use build/testsave, never save/.

Credits

The replacement dialogue font is Crimson Pro by the Crimson Pro Project Authors, under the SIL Open Font License 1.1 (tools/fonts/CrimsonPro-OFL.txt). runtime/font_text.h is generated from it by tools/mkfont_ttf.py.

Sharing it

The recompiler, runtime and tools are original code. gen/ (the translated game code) and data/ are derived from the copyrighted game, so share the source tree and let players run make data / make gen against their own discs, rather than publishing gen/, data/ or a prebuilt binary that bundles them.

Status

Working: boot logos, title menu, intro movie (Cinepak + audio), prologue, CD music, sound effects, the opening scene and dialogue. See NOTES.md for what has and has not been tested yet.

Continuous integration

.github/workflows/build.yml builds the runtime and tools on Linux (Debian trixie), macOS (Homebrew) and Windows (MSYS2 UCRT64, clang) against ci/stub-gen, a stand-in for gen/ with no game code, and runs ci/smoke.sh. The playable game is only ever built locally from your own discs.