EmptyEpsilon is a free and open source multiplayer spaceship bridge simulator — a co-operative game in which each player takes a single station on a starship bridge and the crew has to work together to fly, fight and survive. Rather than one person controlling a whole ship, every officer gets a dedicated screen: Helms steers and manages the thrusters, Weapons fires and controls shields, Engineering allocates power and repairs subsystems, Science runs long-range scans, Relay handles communication, repairs and remote probes, and the Captain — with no station of their own beyond the main view — has to trust the crew’s reports and give the orders.

It began as an open source answer to Artemis Spaceship Bridge Simulator: the developers wanted a bridge sim they could extend themselves, and since Artemis is closed source they wrote their own. The result is written in C++ on the in-house SeriousProton engine with SDL2, and it goes further than the game that inspired it — a live Game Master screen, multiple AI factions, and scenarios scripted in Lua. Development is led by Daid and Nallath and has been public for over a decade; the latest release is EE-2024.12.08.

Key Features

• One station per player — Captain, Helms, Weapons, Engineering, Science and Relay, each with its own specialised interface, so a full crew genuinely has to talk to each other.
• Playable with 1 to 6 people — run several stations on one machine and switch between them with the on-screen button when you are short of players.
• Three combined stations for small crews — Tactical (helms + weapons), Engineering+ and Operations let three or four officers run a full ship.
• Game Master mode — a dedicated GM screen can spawn and remove AI ships and stations, change their configuration, place hazards and talk to the players mid-game.
• Lua mission scripting — scenarios are written in Lua against a documented API, so a GM can build scripted events and whole custom campaigns.
• Multiple AI factions — friendly, neutral and hostile fleets with their own ships and behaviour, plus bought-in 3D models for the larger hulls.
• Networked play on a LAN or the internet — the server listens on TCP port 35666, and stations can be laptops, desktops or Android devices with one shared main screen or projector.
• No store, no account, no cost — free downloads, GPL-licensed source and no monetisation or telemetry.

Why Use EmptyEpsilon?

Most multiplayer games put every player in their own ship; EmptyEpsilon puts a whole crew in one ship and makes communication the core mechanic. Nobody can see the full picture — the helms officer does not know what Science has scanned, and the Captain only knows what the crew tells them — which produces a kind of co-operation few other free games do. It is also unusually flexible for a party game: it runs on ordinary laptops and phones, works over a home LAN, supports one to six players and can be reshaped on the fly by a Game Master. And because it is open source with Lua scripting, it is a realistic project to extend rather than just play.

Use Cases

• Run a bridge night with friends — a few laptops, one TV or projector and a stable network is the whole setup.
• Play solo or in a pair with the combined Tactical and Operations stations when you cannot gather a full crew.
• Set up an internet game over port 35666 with voice chat for crews that cannot meet in person.
• Act as Game Master and script a custom scenario or story for an experienced group.
• Use the Android client to turn spare phones and tablets into bridge stations.
• Study or extend a real, long-running open source C++ game engine with a Lua content API.

Platforms

Windows · Linux · Android. Official releases are published on GitHub: a self-contained Windows ZIP that needs no installation, a Linux .deb package (requires the freetype and SDL2 packages) and an Android APK, currently described as beta quality and built for ARM devices. The engine is cross-platform and can be built from source using the build instructions in the project wiki; all players must run the same version to connect to a session.

Licence

Free and open source: the game and engine source code are released under the GNU General Public License, version 2. EmptyEpsilon is a 100% free game with no paid tier or feature gating; the developers accept donations to buy additional 3D models for the project.

Website

daid.github.io/EmptyEpsilon · source code (GitHub) · downloads

Similar in the directory

• Space Station 14 — another open source multiplayer game built around everyone operating one shared vessel in a role, rather than flying their own ship.
• Endless Sky — open source space combat and trading, if you want the starship setting without needing a full bridge crew.