Heroes of Might and Magic III (1999) rewritten for browser and phone with Opus

Heroes of Might and Magic III, rewritten from scratch for the browser. It plays on a computer and on a phone held either way. Fully implemented rules, early playable AI.

Gameplay demo (phone upright, 3 minutes, with sound): picking a scenario, recruiting a hero, building a building, upgrading a stack, levelling up, splitting stacks, a battle with tactics and spells, capturing a map object, ending a turn.

The game is fully playable end to end; the AI is still relatively weak. Every hour of playtesting still turns up small interface glitches and mechanics to bring closer to the original.

The original's screens, laid out again for a phone: panels you can move and reshape, towns in one column, and a touchpad that aims in battle.

Games are kept on your server as you play. Close the browser on your computer, open the game on your phone, and you are where you left off.

Not a demo with a few units: the full game of Shadow of Death and Horn of the Abyss.

A scene is a map or a battle just big enough to show one thing working (1,290 in all): each creature fights on both sides, so it is used, attacked and attacks you. Each is played headless and checked on every change: docker compose exec game node packages/sim/src/scenecheck.ts (maps) and … battlecheck.ts (battles). Open one in the game: http://localhost:8080/#map?map=scene:spell-0 (or scene:artifact-5, scene:building-12, scene:object-40...). The AI column counts what the computer players did in the AI's own check games (packages/sim/src/aicheck.ts).

Not as good as the original's yet, but at least it doesn't cheat.

The AI is the youngest part of the game and its weakest. An experienced player will beat it.

• It doesn't cheat. The original game's computer sees the whole map, every army's exact size and every garrison. This AI sees only what a human in its seat would see: explored ground, monsters and garrisons by their band ("a pack", "lots"), rival heroes only while in sight, and none of a rival's resources.
• It plays a battle out before choosing it. Each fight is played on a copy of the game by the same battle AI. A stack it knows only by its band is tried at several counts within that band.
• It builds by return. It picks each building by how fast it pays back toward the Capitol and the top dwellings, saving up and trading at the market when that's worth it.
• It values what a passage opens. A guard, a garrison, a key or border gate, a boat, or a monolith into unexplored land is worth what lies behind it.
• One main hero carries the army and takes the experience. The other heroes gather resources and bring it troops.
• It casts adventure spells: View Air/Earth, Dimension Door, Fly, Water Walk, Town Portal, Summon/Scuttle Boat, Disguise, Visions.
• It never surrenders, as in the original. It can retreat.

The AI in every seat on the original's own maps, nobody watching: eight players on Free for All and on Realm of Chaos, both still open after 200 days, and two on Key to Victory, won on day 90.

docker compose exec -e RACE_ENGINES=fresh game node packages/sim/src/race.ts --map "Free for All.h3m" --days 200 --seed 1 > race.json plays such a game headless: each side's towns day by day and the milestones it reached.

• Its rule tweaks and quality of life: re-implemented here , in every game.
• Its content and art (the Cove, Factory and Bulwark towns, their creatures and heroes, the new objects, its maps): only when you provide the files (see below).

You may not want to run a repository from the internet just because it looks exciting. Here is what this one does to your machine; each point can be checked in the files it links.

1. Everything runs in one unprivileged container. The game's server runs in Docker (compose.yml ,Dockerfile ) as the image's usernode , not root, with no Linux capabilities,no-new-privileges and a read-only file system. It writes only to its own two Docker volumes (the unpacked game files and your saved games) and a scratch/tmp , reads yourinstallers/ folder read-only, and sees nothing else of your machine. It listens on127.0.0.1:8080 only, unless you setBIND .
2. The build fetches pinned, checked files, and uses none of your accounts.docker compose up --build downloads the Node base image by its sha256 digest; the npm packages at the exact versions inpackage-lock.json , each checked against its sha512; VCMI's and the HotA mod's data files from GitHub at fixed commits, each checked against its sha256 inpackages/vcmi-data/sources.json (a mismatch stops the build); and three Debian packages (innoextract to unpack the installers, ffmpeg for the game's videos, git for language packs) from Debian's signed archive. No login, token or key of yours is asked for or used, and nothing is uploaded.
3. Running, it calls out only when you ask. The server makes no outside requests: no telemetry, no accounts. The one exception is a language pack, fetched from its GitHub repository at a fixed commit when you pick it on the setup page.
4. Few npm packages, pinned, none fresher than a week. No package's install script ever runs (.npmrc 'signore-scripts , andnpm ci --ignore-scripts in the Dockerfile). Every version in the lockfile had been on npm for at least 7 days when it was taken (supply-chain attacks are usually caught and pulled within days), andmin-release-age=7 in.npmrc keeps it so. The running server loads one of them,ws ; the rest only build the page (TypeScript, Vite, PixiJS).

It contains no game files: they come from your own copy of the game.

1. Put the installers in the installers/ folder.

2. `docker compose up --build`
3. Open [http://localhost:8080](http://localhost:8080) .

The first start unpacks the installers into a Docker volume (a few minutes); later starts are immediate.

Then open http://localhost:8080/setup: it shows what was found in your installers and which languages the game speaks with them.

Or ask your coding agent: "Set this up with my installers and start it." Everything it needs is in this file, compose.yml and setup/.

The game's own menus and windows come in English, Polish, German, Russian, Ukrainian, French and Spanish. The original game's texts come from your installer, in its language; the HotA installer adds Russian. For another language, the setup page offers community translations made for VCMI, fetched from their own repositories onto your server only (none is part of this repository; their licences are their authors'):

| Language | Translation |

|---|---|
| Polski | [https://github.com/vcmi-mods/polish-translation](https://github.com/vcmi-mods/polish-translation) | 
| Deutsch | [https://github.com/vcmi-mods/german-translation](https://github.com/vcmi-mods/german-translation) | 
| Français | [https://github.com/vcmi-mods/french-translation](https://github.com/vcmi-mods/french-translation) | 
| Español | [https://github.com/vcmi-mods/spanish-translation](https://github.com/vcmi-mods/spanish-translation) | 

Without the page: docker compose exec game node setup/pack.ts pl. Then pick the language in Options → Language.

No server needed: your own computer is enough, once.

1. Start it on your computer as above.
2. Open it on the phone over HTTPS. Browsers keep a page's files on the device only for HTTPS pages, so http://192.168.…:8080 won't do. One free way isTailscale on both devices andtailscale serve 8080 on the computer: the phone opens thehttps://….ts.net address it prints. SetPUBLIC_HOST to that name.
3. On the phone: ☰ → Play offline. The whole game is kept on the phone, and a single-player game goes on with no connection at all, on a train, abroad, with the computer switched off.

To play from anywhere with a connection too (cloud saves, multiplayer), run the same container on a server of yours, behind a login such as Tailscale or a reverse proxy with a password: whoever can open the page can play on it and fetch the game files from it.

Written from scratch in under two weeks by a group of Claude Opus 5.5 agents in Claude Code, guided by about 40 hours of human play and feedback so far, mostly the author's, plus a handful of friends. Estimated use: roughly 200 million tokens.

This is a release of the source, as it is. There are no issues, pull requests or support: fork it if you want to change it. It works for us with the installers above; other versions of the game may need changes.

Heroes of Might and Magic is a trademark of Ubisoft. Horn of the Abyss is the work of the HotA Crew. This project is not associated with or supported by Ubisoft or the HotA Crew; it reads your own copy of the game and contains none of

its art, sounds or texts. Many rules and layouts were checked against VCMI ([https://vcmi.eu](https://vcmi.eu)), the open-source engine
for Heroes III, and the Heroes III wiki ([https://heroes.thelazy.net](https://heroes.thelazy.net)).

MIT (see LICENSE). That covers this repository only. What the build fetches keeps its own licence and is not part of it: VCMI's config files (GPL-2.0-or-later) and VCMI's Horn of the Abyss mod (CC BY-SA 4.0), from which the image makes its data tables (packages/vcmi-data), and the language packs the setup page fetches. Your game files stay yours.