A2 Racer 4 – De politie slaat terug! in the browser

Play it: https://games.nostalgiarealm.com/a2racer4/

Version 1.1.7. Changelog, release notes. Downloads: GitHub, GitLab. Repositories: GitHub, GitLab.

A port of the Dutch racing game from 2000 to WebGL and Three.js, built from the original game files. The race itself is the original code: spel.dat is recompiled from x86 to WebAssembly, so its physics, AI, rules and HUD logic run as shipped. The menu is rewritten by hand from the original forms and code. All artwork, music, speech and text are the originals, in Dutch.

Status, measurements and what was checked: docs/feature-parity.md, docs/validation.md. Changes on purpose: docs/intentional-differences.md. Continuing the work: docs/LLM_GUIDE.md, PLAN.md. All documents: below.

The game's content is in the port, with Davilex's two official updates, track 9 (the Country etappe) and car 7 (the truck De Schaduw), and with the gaps listed under Known incomplete in docs/feature-parity.md. The race runs the fixes of the owner's Windows patch A2-Racer-4-Fixes that matter at its 60 ticks per second, parts 11 to 13, from his own code: tools/recomp/owner-fixes/. 3D kaart off works: Normaal and Laag then run the race's 8-bit software path, 640x480 and 320x200. Verification covers one level, etappe 0 (Amsterdam), in headless Chromium on a desktop GPU. Other levels have a boot check at most, and the Country etappe with the truck one launch on top. No real phone, tablet or gamepad and no other browser engine was tried. On that level the original spel.dat also ran under Wine, and the port's speeds, reverse, brake, countdown, first time steps and three frames of its picture were set against it. The 8-bit path, which Wine cannot run, ran on an emulated Windows 98 machine, and the port's frames at rest were set against it pixel by pixel: 88.1% of the picture identical at 640x480 and 85.5% at 320x200. Steering, turbo, damage, collisions, the end of a race and traffic were not measured on the original, and no real hardware of the period was used. The original has not been run with the updates; for Amsterdam with car 0 the data is the same.

Downloads

Desktop builds for Linux, Windows and macOS, a static web build, the source and the decompile: docs/releases/ lists the files of each release and what was checked on each. The Windows package has run under Wine but not on Windows, and the macOS packages have not been started so far.

The decompile of the original game is in original-game-decompiled/: generated C and assembly of every game module, unpacked resources, Ghidra projects, format documents and the game's own files. What is left out, such as the disc image and third-party installers: docs/releasing.md.

Run it

You need Node.js 24. The prepared files in public/ are already in this folder. npm ci also rebuilds rcs.img from its pieces in large-files/, because it is too big for one file in git.

npm ci

npm start

Open http://127.0.0.1:4180/. Click once: that allows sound and enters full screen. Another port: PORT=8080 npm start.

Development

npm run dev does the same as npm start: it bundles source/ into public/src/ once and serves public/. There is no watch mode. After editing source/, bundle again and reload the page:

npm run bundle

Desktop

The same game in Electron, with its files inside the package. npm run desktop starts it from this folder. npm run desktop:linux and npm run desktop:win build the packages into release/. macOS comes from .github/workflows/macos-release.yml. The quit path in the menu returns to the first screen, as in the browser: close the window to leave. Releases: docs/releasing.md.

Controls

Action	Keyboard	Gamepad	Touch
Steer	Left, Right	Left stick or D-pad left, right	Wheel, left and right
Gas	Up	RT or A	Wheel, upper half
Brake, then reverse	Down	LT, B, D-pad down or stick down	Wheel, lower half
Turbo	Ctrl	X	Turbo
Handbrake	Alt	RB	Handrem
Horn	Space	Y	Claxon
Cameras	1, 2, 4, also 6 to 0	LB, next of 1, 2, 4	Camera, next of 1, 2, 4
Look back, while held	3	R3	Terugkijken
Reset	Enter	L3	Reset
Roepen	T	D-pad up	Roepen, under Meer in landscape
Dashboard	5		Dashboard, under Meer in landscape
Overlay detail	D		Detail, under Meer in landscape
Pause	P, then any key or a mouse button on the race	Start, then A, B or Start	Pauze, then Verder or a tap on the race
Quit	Esc, then J or Y. Esc or N stays	Back, then A or B	Stop, then Ja or Nee
Leave finish table or game over	Esc, Enter or Space	A	Verder
Full screen	On at the first gesture. Leaving it turns the setting off and, in a race, opens the quit prompt. With a mouse in full screen: Stop beside the gear
Settings	In a race F9, also closes; Esc closes. In the menu Opties, Geavanceerd, tab Browser		In a race the gear button. In the menu the same dialog
Menu	Mouse and keyboard, as in the original	D-pad or stick moves, A is Enter, B is Esc, RB is Tab	Tap

The keys in the first six rows are the Standaard values and can be changed in Opties. The others cannot, as in the original.

The game has no reverse gear or gear keys. Holding brake at a standstill is how it reverses, as in the original.

On macOS, Ctrl+Left and Ctrl+Right switch desktops, so bind turbo elsewhere in Opties.

Both settings places hold 3D-resolutie, Renderschaal, Volume, Beeldjes per seconde tonen, Volledig scherm, Aanraakbediening and Deadzone gamepad. They are saved per browser. No pad button opens them.

Touch controls show on a touch screen, or with Aanraakbediening on. A pad connected at race start drives that race; one found later works from the next race. The race pauses if the pad in use goes away.

Prepare from the original game

Only needed for a fresh copy without public/assets and public/game. Inputs stay unchanged. They come from original-game-decompiled/, the decompile package made from the installed game and its disc; see its own README.md to rebuild that. The owner installed Davilex's two updates after that package was made: prepare-assets.py lays original/updates/installed/ over original/install/, and the updates win. Re-run the input fingerprints before trusting that snapshot of the install: docs/LLM_GUIDE.md, "The snapshot is not the installation".

python3 tools/prepare-assets.py

python3 tools/convert-dfm.py

~/.local/share/reverse-engineering/python-analysis/bin/python -I tools/recomp/build.py --no-ret-store

node tools/build-race-lists.mjs

Step	Result
prepare-assets.py	public/assets: race files, menu art as PNG, Hunny's frames, help text, error icon, H.264 video, wait pictures, progress bar frames, for the 8-bit path too, touch art from source/assets/touch, and asset-map.json from output to source, 764 entries. Video needs ffmpeg with libx264
convert-dfm.py	public/assets/menu/forms.json: the decoded Delphi forms
recomp/build.py	public/game/spel.wasm, spel.meta.json. Needs Python with capstone; npm run recompile runs this same command. See docs/recompiler.md
build-race-lists.mjs	public/assets/game/race-files.json: what each race reads from the archives, with soft[0] and soft[1] for the 8-bit modes. Needs spel.wasm

Options of prepare-assets.py:

python3 tools/prepare-assets.py --skip-video

python3 tools/prepare-assets.py --only help,loading-bar,touch,error-icon

--only runs the named steps and keeps the other entries of the asset map. The steps are race, menu, error-icon, agent, help, loading, loading-bar, touch and media. --skip-video leaves the videos out of media. A video whose MP4 already exists is not converted again, with or without it: delete the MP4 to redo it.

Build a static site

npm run build

npm run preview

dist/ is plain static files. The server should support HTTP range requests for rcs.img and rc.img; nginx, Apache and GitHub Pages do. Without them each read fetches the whole archive. Only tools/serve.mjs was run.

Checks

The browser tools need Chromium for Playwright, once:

npx playwright install chromium

They do not start a server or bundle anything. Have npm start running in another terminal, on a fresh bundle.

Command	What it does	Needs a server
node tools/check-flow.mjs --speed 8 --timeout 400	Real clicks from the intro through a whole bot race on Amsterdam to the results and back. Writes evidence/flow/	Yes
node tools/check-race-ui.mjs	76 named input, focus, settings and layout checks. Writes evidence/race-ui/summary.json. --only touch,keyboard,touchsetting,results,gameover,gamepad,failure,intro runs those sections	Yes
node tools/check-software.mjs	The 8-bit path with real clicks: 3D kaart off and on, a whole bot race at RESOLUTION 1, a short one at 0, back on with the 3D card. 17 named checks. Writes evidence/software/flow/	Yes
node tools/benchmark.mjs --gpu --throttle 8 --seconds 60 --warm 12 --out evidence/performance/final-8x.json	The mobile performance measurement: 800x360, DPR 2, 8x CPU throttle. Without --gpu it uses software rendering	Yes
node tools/benchmark.mjs --gpu --throttle 8 --seconds 60 --warm 12 --url 'http://127.0.0.1:4180/?race=1&bot=1&bench=1&nostatic=1' --out evidence/performance/final-before-static-8x.json	The same, without the static track vertices	Yes
node tools/benchmark.mjs --gpu --throttle 1 --size 1280x720 --dpr 1 --seconds 60 --warm 12 --out evidence/performance/final-normal.json	Normal rendering, for the comparison	Yes
node tools/benchmark.mjs --gpu --throttle 1 --size 1280x720 --dpr 1 --seconds 60 --warm 12 --frameskip 2 --out evidence/performance/final-normal-30fps.json	Every second display frame, 30 FPS	Yes
node tools/compare-traces.mjs evidence/performance/final-normal.json evidence/performance/final-8x.json	Compares two of those runs per game second: the checksum over every object with a physics body, and position and speed of the player's car	No
node tools/check-driving.mjs --json evidence/driving/amsterdam-no-opponents.json	Scripted driving, no opponents, prints speeds. Repeatable	No
node tools/check-owner-fixes.mjs --out evidence/owner-fixes/races-with-fixes.json	Whole bot races on all 10 etappes, reading the state of the owner's added code: 25 Hz tick, camera, hung_check. --game points at another build	No
node tools/check-shadow.mjs --hz 144 --out evidence/shadow/summary-144hz.json	The player's shadow in its car's frame per presented frame, with the bot on Amsterdam. --hz stands in for a display rate	Yes
node tools/check-wheels.mjs --hz 144 --out evidence/wheels/summary-144hz.json	The wheels' matrices as drawn between ticks, with the bot on Amsterdam: 1 is a wheel at its own size	Yes
node tools/check-hud-spray.mjs 900	The HUD in every frame with 900 extra world-matrix rows taken per tick, as a dense spray does	Yes
node tools/check-pairing.mjs --etappe 7	Every draw's pairing with the tick before against the nearest free draw of its mesh, per mesh	Yes
node tools/check-lights.mjs --etappe 7	How the renderer pairs the car lights between ticks: lights paired with another light	Yes
node tools/check-tail-glow.mjs 165 7 20	The player's tail-light glow against its car per presented frame, at a 165 Hz stand-in	Yes
node tools/check-traffic.mjs --hz 60	Traffic nose rise on the owner's method. Also --hz 30 and --whole-push, one JSON line each; evidence/traffic/nose-rise.jsonl holds the four	No
node tools/run-bot.mjs	A whole race in Node with opponents and traffic. Prints progress and what it writes to game.ini	No
node tools/build-race-lists.mjs	Boots all 10 etappes with all 8 cars for 2 s, and all 10 at RESOLUTION 0 and 1, to list the files each race reads. Not a gameplay check	No
node tools/run-headless.mjs --ticks 300	Runs the race in Node without a browser. npm run test:headless	No
node tools/check-phone-flow.mjs	The flow with taps on an emulated phone: menus at 844x390 and 390x844, a race on the wheel, Stop and Ja, the Tour's screens up to the Garage. No whole race. 7 checks. Writes evidence/flow-phone/	Yes
node tools/contact-sheet.mjs	The bot drives; a screenshot every few seconds. Writes evidence/smoke/	Yes
node tools/shot.mjs --url "http://127.0.0.1:4180/?form=TfrmGarage" --out evidence/forms/garage.png --size 1280x720 --wait 2500	One form or page in a screenshot, on software rendering. --mobile for touch and DPR 2	Yes

A race without the menu: http://127.0.0.1:4180/?race=1&etappe=9&car=7, default etappe 0, car 0. &resolution=1 or 0 starts the 8-bit path, and &chunks=15 sets the view distance for comparing with a slow machine. pinRace in source/host/race-setup.js sets those keys in game.ini and raser.ini, because the car update's copy comes from the developers' machine. The Node tools do the same, and read their files from public/assets/game.

Comparing two runs: compare the movement state first. The player's car accelerates by the movement state of its five physics cores, which latch in the first 0.2 s of a launch. At 4 s that is about 20.7 m/s with all cores in state 1 and about 17.3 with all in state 2, and there are mixes. It is the game's own spread, in the original as in the port, and the moment of the gas does not decide it in the original. So a speed difference between two runs says nothing until their states match: movementState in the JSON of check-driving.mjs, the state strings of analyze.py regimes below. Results: docs/validation.md.

Reference runs of the original

These run the original spel.dat under Wine on Amsterdam and read its memory per tick, with the same key scripts on the port. They need Wine, Xvfb and Python on the host, no server and no bundle. They use a private Xvfb and a throwaway Wine prefix, and never touch ~/.wine or the original files. Their copy of the install has no updates, which for Amsterdam with car 0 is the same data. All commands: tools/reference-wine/README.md. Report: evidence/reference-wine/results.md.

Once, to create the prefix:

systemd-run --user --scope -q -p MemoryMax=4G -p MemorySwapMax=0 tools/reference-wine/prepare.sh

One start of the original, held to 60 ticks per second from outside:

tools/reference-wine/run.sh --name launch-a --pace 60 --gas-at go+0.5 --gas-for 12 --after 0.5

The same on the port:

node tools/reference-wine/port-launch.mjs --name port-launch-a --gas-at go+0.5 --gas-for 12 --after 0.5

The tables:

python3 tools/reference-wine/analyze.py regimes evidence/reference-wine/raw/launch60-*.json.gz -- evidence/reference-wine/raw/port-launch60-*.json.gz

Everything the report is based on, about 20 minutes:

tools/reference-wine/campaign.sh

The 8-bit path cannot run under Wine. tools/reference-86box/ runs it on a throwaway copy of the owner's 86Box Windows 98 machine and takes screenshots of the guest, and sets the port's frame against them. All commands: tools/reference-86box/README.md. Report: evidence/reference-86box/results.md. Findings: docs/research/render-8bit.md.

Folders

Folder	Content
source/	Maintained code: host/ Windows and DirectX in JavaScript, render/, audio/, input/, menu/, ui/, dev/ the test bot, assets/touch/ the touch art
tools/	Asset preparation, recompiler, server, build, checks; reference-wine/, the runs of the original under Wine; reference-86box/, its runs on the 8-bit path on an emulated Windows 98 machine
public/	What the browser loads. Generated: rebuild with the commands above
dist/	The static site from npm run build
original-game-decompiled/	The decompile package: original files, recovered code, its documentation; original/updates/, Davilex's two updates: the EXEs, the installed files, delta.csv
docs/	Documents, see below
evidence/	Measurements and screenshots; software/, the 8-bit path; reference-wine/, the runs of the original under Wine; reference-86box/, its frames on the 8-bit path

Documents

Document	Content
CHANGELOG.md, docs/releases/	Versions, release notes
docs/releasing.md	What a release contains, what stays out, how to make one
docs/hosting.md	The live site: server, Nginx, how to update it
docs/request.txt	The brief
PLAN.md	Milestones, progress, blockers, next actions
docs/LLM_GUIDE.md	Folder map, boundaries, entry points, debug routes, how to continue
docs/original-behavior.md	What is established about the original, and how
docs/behavior/	The same per area, with evidence: audio, host, hud, input and platform, race rules, render, simulation and timing, start-up and menu
docs/feature-parity.md	Content and features, implementation and verification status
docs/parity/	The same per area: audio, host, hud, input and platform, race rules, render, simulation and timing, start-up and menu
docs/validation.md	Test procedures, results, environments, known discrepancies
evidence/reference-wine/results.md	The original under Wine against the port: setup, tables, what is not established
evidence/reference-86box/results.md	The original's 8-bit path on an emulated Windows 98 machine against the port: frames and numbers
docs/intentional-differences.md	Requested adaptations and their effect on original behaviour
docs/provenance.md	Every executable, installation against disc, which files are the authority, configuration, saves, reference environment
docs/reuse.md	What was taken from the RedCat ports, and what differs
docs/recompiler.md	How spel.dat becomes WebAssembly
docs/research/	Reverse-engineering notes per subsystem, with corrections at the top of each note that has known errors. render-8bit.md is the 8-bit path as measured
source/menu/README.md	How a menu form is written
original-game-decompiled/README.md	The decompile package, with its own LLM_GUIDE.md

Rights

The game, its code, media and fonts retain their owners' rights. This project is not affiliated with Davilex. Extraction does not imply ownership or a redistribution licence. The code in original-game-decompiled/decompiled/ is generated pseudocode, not the developers' source. This project's own code carries no licence grant.