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Alien Resurrection: Recompiled

The PlayStation's Alien Resurrection, running natively on macOS, Windows and Linux

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Alien Resurrection: Recompiled is a native port of Alien Resurrection (PlayStation, USA release SLUS-00633), made by statically recompiling the game's MIPS code. The game runs on a small runtime that stands in for the PlayStation's BIOS and hardware, and a modern GPU renderer draws it in high resolution and widescreen, at a steady 60 fps. It adds precision geometry without the PS1 wobble, mouse and keyboard controls, quick saves and optional gameplay tweaks.

Download the latest release

[!IMPORTANT] This repository and its releases contain no part of the game, neither data nor code. You need your own copy of Alien Resurrection (USA, SLUS-00633) as a disc image (a .cue sheet with its .bin tracks) to play.

PlayStation (240p, 4:3)	This port (16:9, 3x resolution, precision geometry)

The same frame of the first attract demo. The alien at the right edge is only fully visible in widescreen.

Table of Contents

• System Requirements
• Getting Started
• Features
  • Plug and Play
  • Widescreen and Wider Field of View
  • High Resolution
  • Precision Geometry
  • Steady 60 FPS
  • Mouse and Keyboard
  • Responsive Controls
  • Quick Save
  • Settings Without Leaving the Game
  • Sprint
  • Enemy Damage Sliders
  • Infinite Flashlight
  • Smaller Changes
• Controls
• Planned Features
• FAQ
• Known Issues
• Building
• How It Works
• Credits
• License

System Requirements

System	Requirements
macOS	macOS 11 or later, Apple Silicon or Intel
Windows	Windows 10 or 11, 64-bit, a GPU with Vulkan or Direct3D 12
Linux	x86_64 with glibc 2.35 or newer (Ubuntu 22.04, Debian 12, Fedora 36, SteamOS 3 or newer) and a Vulkan driver

If the game does not start, make sure your graphics drivers are up to date.

Getting Started

1. Download the package for your system from the latest release and unpack it.
2. Run AlienResurrection (.app on macOS, .exe on Windows, ./AlienResurrection on Linux).
   • macOS: the app is not notarized. On first launch macOS blocks it; open System Settings › Privacy & Security and choose Open Anyway.
   • Windows: SmartScreen may warn about an unrecognized app; choose More info › Run anyway.
3. Choose Select disc image and pick your Alien Resurrection (USA).cue.
4. Adjust Settings and Controls if you like, then Start game.

Features

Plug and Play

Start the port, choose your disc image (.cue, one of its .bin tracks or the folder) and press Start game. The launcher checks that it is the USA release and shows the title art, read from your own disc. Settings and controls can be changed here or later in game, with the mouse, the keyboard or a controller.

Widescreen and Wider Field of View

• Widescreen at 16:9, 16:10, 21:9 or 32:9 widens the view in 3D instead of stretching the picture. The HUD, menus, loading screens and movies keep their original 4:3 shapes.
• Field of view slider: the game's own view is fairly narrow (53° across the screen at 4:3, 67° with 16:9 widescreen); widen it up to 100°. The first-person weapon keeps its original framing.

High Resolution

• Internal resolution from the original 240p up to 8x (1920p); 4x by default.
• Smooth or sharp scaling to the window, fullscreen, and vsync without tearing.

Precision Geometry

The PlayStation rounds every vertex to a whole pixel and maps textures without perspective correction, which makes polygons jitter and textures warp as the camera moves. Precision geometry (in the spirit of PGXP) keeps the full precision of every projected vertex and its depth, so geometry stays still and textures stay straight. Walls that reach past the camera, which the original draws smeared and bent at the edge of the screen, are clipped properly. It can be switched off for the original look.

Steady 60 FPS

On the original hardware busy scenes drop to 20–30 fps. The port runs the game's code at three times the original CPU speed by default, which keeps 60 fps; the game measures elapsed time itself, so it plays at the same speed as on the console. The game also capped itself at 20 fps while loading the next part of a level (from the terminal or door that starts the load until you walk through); the port stays at 60.

Mouse and Keyboard

Look and turn with the mouse (adjustable sensitivity), move with WASD, fire with the left button. Every PlayStation button can be bound to two keys or mouse buttons and to a controller button on the Controls page. Controllers are detected automatically and start with the PlayStation layout. F1 releases the mouse; clicking the window captures it again. See Controls for the default bindings.

Responsive Controls

In the original the sticks reach the game two frames late and are ignored until pushed 38% of the way; the camera stick only sets a turning speed. The port reads the controls right when the game needs them:

• Mouse look turns the camera directly: every mouse movement turns the view by exactly that much, immediately, with no dead zone and no speed limit.
• Responsive sticks (on by default): both sticks, and the move and look keys, take effect on the next frame, with a 10% dead zone instead of 38%. Half a push on the left stick walks at half speed; the camera stick has a choice of response curves (Linear, Smooth, Precise) and an adjustable speed (150% of the original by default). Turn it off for the original handling.

Sticks, Turn speed 4	Original	This port (defaults)
Frames until the camera or Ripley moves	3	1
Stick travel ignored	38%	10%
Movement with the left stick half pushed	18%	45%
Full-speed turn	137°/s	206°/s

Quick Save

The original only saves at the save stations, and loading one puts you back in front of that station. Quick save (on by default) adds one slot that keeps the exact moment: press F5 anywhere to save and F9 to return to it, with enemies, doors, items and sounds exactly as they were. It works in the title menu too, so a session can pick up where it left off right after starting the game. The keys can be changed in Controls (also for a controller), and the pause menu (F2) has Quick save and Quick load entries. Memory card saves are not touched.

Settings Without Leaving the Game

Press F2 (or hold Select + Start on a controller) to pause and open the settings and controls over the game. Changes apply immediately, except internal resolution, VSync and skipping the intro, which are marked as applying on the next start. Quit to desktop is there too.

Sprint

Hold Shift (or click the left stick on a controller) to move faster. Added by this port: the game's own running speed is scaled, so collisions, doors and slopes behave as usual and the speed ramps up and down smoothly. 190% by default, adjustable from 110 to 250%.

The same four seconds from the start of level 1: running (left) and sprinting at 190% (right).

Enemy Damage Sliders

Make the game easier or harder: Settings › Enemy damage has an "All enemies" percentage and one for each kind of enemy (alien warriors, facehuggers, chestbursters, the queen, the Newborn, marines and soldiers, the sentry tank, and acid blood), from 0 to 200%. The game's own difficulty setting still applies on top. Falls, drowning and your own explosions are not affected.

The same alien attack. Left: original damage, Ripley goes down after five hits. Right: enemy damage at 50%, she is still standing.

Alien warrior hit, Normal difficulty	Health lost	Hits to go down
100% (original)	24%	5
50%	12%	9
200%	48%	3

Infinite Flashlight

The flashlight (from the second level on) normally lasts about 20 seconds and then has to recharge while switched off. With Infinite flashlight (on by default) the battery never runs down.

Original, 20 seconds after switching it on	Infinite flashlight

Smaller Changes

• Memory card saves work (save, load, overwrite) and are kept as standard memory card images.
• Skip intro movies starts straight at the title menu.
• Fast forward: hold the backtick key.
• Invert Y is off by default (the original defaulted to on); the game's own option still changes it.
• Screenshots with F12.

Controls

The game uses the DualShock "Dual Stick" scheme (left stick moves and strafes, right stick looks and turns). Default keyboard and mouse bindings, all changeable in Controls:

Key	Pad	In game
W A S D	left stick	move / strafe
Shift (hold)		sprint (added)
mouse (click window to capture, F1 releases)	right stick	look / turn
arrows	d-pad	menu navigation, look / turn
left click / Left Ctrl	R1	fire
right click / F	R2	action
E	Circle	use
Space / C	Cross	menu accept, crouch
X / Backspace	Triangle	menu back, next item
Z	Square	previous item
R / Q	L1 / L2	next / previous weapon
Esc / Enter	Start	pause
Tab	Select	look hold
V / B (middle click)	L3 / R3	centre view / quick turn
` (backtick)		fast forward (added)
F5 / F9		quick save / quick load (added)

Fixed keys: F2 opens the settings overlay, F11 or Cmd+Ctrl+F toggles fullscreen (F11 only on Windows), F12 takes a screenshot (Shift+F12 dumps VRAM), F1 releases the mouse. These can't be bound to game actions. Quit with Cmd+Q (Alt+F4 on Windows), by closing the window, or with Quit to desktop in the overlay.

Controllers are detected automatically; their sticks always drive the analog sticks and the buttons follow the Controls page (default: the PlayStation layout, left stick click = sprint, which latches until the stick returns to centre; the game's L3 "centre view" is on V). Holding Select and Start together opens the overlay; neither button reaches the game then, so the game's own pause menu stays closed.

Planned Features

• High-resolution texture replacement. The game's art can't simply be swapped for bigger images: textures are small 4-bit tiles packed into 256×256 VRAM pages, each drawn with its own 16-colour palette (see Textures and images). The plan, as in emulators such as DuckStation, is to dump every texture the game draws to PNG (named by a hash of its pixels and palette), let them be upscaled or repainted, and have the renderer draw the replacements. Full-screen images (loading screens, title art) can be replaced whole.
• Linux: an AppImage or Flatpak for desktop integration, and arm64 packages (they build with ARCH=arm64 tools/build_linux_docker.sh but are not part of the release yet).

FAQ

What is static recompilation?

Translating a program's machine code into another language ahead of time instead of emulating it while it runs. tools/recomp.py turns each of the game's roughly 2,000 MIPS functions into a C function, which is compiled for your computer together with a runtime that replaces the PlayStation's BIOS and hardware.

Why do the downloads interpret the game's code then?

The recompiled C is derived from the game, so it can't be distributed. The downloads read the game's code from your disc image when you play and run it with the port's MIPS interpreter, with exactly the same enhancements. Building from source with your own disc gives you the recompiled version (see Building).

Is this an emulator? Can it run other games?

No. The runtime only implements what Alien Resurrection uses, and the port only accepts the USA release (SLUS-00633). Other games, and other releases of this one, are not supported.

Is this based on a decompilation?

No. The port runs the game's original code unchanged; its enhancements are small native replacements for individual game functions, found by reverse engineering the game. What has been learned so far is in docs/FINDINGS.md.

Where are my saves and settings?

Memory cards (standard 128 KiB images), config.ini and the quick save (quicksave.state) live in:

System	Folder
macOS	~/Library/Application Support/AlienResurrectionPort/AlienResurrection/
Windows	%APPDATA%\AlienResurrectionPort\AlienResurrection\
Linux	~/.local/share/AlienResurrectionPort/AlienResurrection/ (or under $XDG_DATA_HOME when set)

The game keeps its own options (Invert Y, crosshair, vibration…) inside each memory card save and restores them from the newest save at startup. Delete quicksave.state to start without a quick save; copy it to keep one aside.

Why won't my quick save load after an update?

A quick save is a snapshot of the whole emulated PlayStation (about 4 MB) and belongs to the version of the port that made it. Before updating, save at a station; memory card saves carry over.

Can I get the original look and feel back?

Yes: in Settings turn off Widescreen, Precision geometry, Responsive sticks, Sprint and Infinite flashlight, and set Internal resolution to 1x, Field of view to Original and Frame rate boost to Original (100%).

Where do I report a bug?

In the issue tracker. On Windows, alien.log in the save folder (above) has details when the game fails to start.

Known Issues

• No rumble output: the DualShock rumble protocol is implemented but not passed on to controllers.
• The PlayStation Mouse, which the game supports, is not emulated.
• The Windows build has been verified under Wine and in a Parallels VM, and the Linux build in containers; reports from native Windows and Linux machines are welcome.
• Not every level has been played through on the port yet.

Building

Building is not required to play: the releases have ready-made packages, which contain no game data or code. To build the port yourself, as a recompiled build from your own disc or as the interpreted build the releases use, see docs/BUILDING.md. It also covers the release workflow and the command-line options used for testing.

How It Works

• tools/recomp.py translates every MIPS function of the two game executables (the boot loader and ALIEN.BIN) into C, one C function per MIPS function. Sony's PsyQ library functions are identified by signature. Release builds instead interpret the original machine code read from the player's disc, calling the same native hooks.
• The runtime (src/runtime, src/hw) replaces the PlayStation BIOS and models the hardware the game and its libraries talk to: GPU, GTE, CD-ROM, SPU, MDEC, DMA, timers, controllers and memory cards.
• The renderer (src/render) draws the game's GPU commands through the SDL3 GPU API (Metal on macOS, Vulkan or Direct3D 12 on Windows, Vulkan on Linux), at a multiple of the original resolution.
• The enhancements are small native replacements for individual game functions (src/runtime/native.c), found by reverse engineering the game.

See docs/ARCHITECTURE.md for how the port works and docs/FINDINGS.md for what has been learned about the game so far.

Credits

• SDL3 for windows, input, audio and the GPU API.
• Dear ImGui for the launcher and the in-game overlay.
• psx_psyq_signatures for identifying Sony's library functions.
• Architecture of Consoles by Rodrigo Copetti, for PlayStation hardware reference.
• PGXP, originally by iCatButler for PCSX-R, for the idea behind precision geometry.

License

The port's own source code and documentation are released under the MIT License. That covers only what was written for this project:

• third_party/imgui is Dear ImGui, under its own MIT license (third_party/imgui/LICENSE.txt); SDL3 is used under the zlib license.
• Alien Resurrection itself (its code, data, artwork, text, music and trademarks) is not covered and not included. The screenshots and animations in docs/media show the game and remain the property of its owners; they are here only to illustrate the port.
• The C code that tools/regen.sh recompiles from your disc (src/gen/) is derived from the game, is not covered by this license and is not part of the repository. Recompiled builds contain it and are for personal use; the release packages are interpreted builds, which contain no game code and read it from the player's own disc image.

This is an independent fan project, not affiliated with or endorsed by 20th Century Studios, Fox Interactive or Argonaut Games. Alien Resurrection and all related game content belong to their owners; no game data is included.