0 A.D.

0 A.D. is an open‑source real‑time strategy (RTS) game that offers a fully self‑hosted multiplayer experience. From a technical standpoint, it is built around a client–server architecture where the authoritative game state is maintained on a dedicated server instance. The server can be run on any platform that supports the game’s C++ runtime, allowing developers to host sessions in data centers, on-premises hardware, or within containerized environments such as Docker or Kubernetes. The game’s networking layer is a custom protocol optimized for low latency, packet loss tolerance, and deterministic simulation across heterogeneous client hardware.

• Deterministic Simulation: The game engine uses lockstep simulation for all physics and AI, ensuring that every client processes the same input sequence to produce identical world states. This is critical for competitive multiplayer and simplifies debugging of network inconsistencies.
• Modular Asset Pipeline: All game assets (textures, sounds, scripts) are stored in a simple directory hierarchy and can be hot‑reloaded by the server. This makes it straightforward to develop custom maps or unit types without recompiling the engine.
• Extensible Scripting: The core scripting language is JavaScript (via a lightweight engine), exposing a rich API for AI, event handling, and UI customization. Developers can write custom game logic or bots that run on the server or client side.
• Plugin Architecture: A plugin system allows developers to inject C++ modules at runtime. Plugins can hook into the rendering pipeline, modify AI behaviors, or add entirely new gameplay mechanics.

• Languages: C++17 for the engine core, JavaScript for scripting, and GLSL/HLSL for shaders.
• Graphics: OpenGL 3.3+ (cross‑platform) with optional DirectX 11 support on Windows.
• Audio: OpenAL for spatial sound; FMOD is an optional commercial backend.
• Networking: Custom UDP‑based protocol with built‑in sequence numbers and reliability layers; optional TLS encryption via OpenSSL.
• Database: None required for core gameplay. Optional SQLite or PostgreSQL can be used to persist player statistics, leaderboards, or matchmaking data when integrating with external services.
• Build System: CMake 3.10+ with Ninja or Makefile generators; continuous integration via GitHub Actions.

• Self‑Hosting: The server binary is a single executable with minimal dependencies, making it ideal for lightweight VMs or bare‑metal hosts. It listens on a configurable port (default 7777) and supports TLS, authentication tokens, and rate‑limiting.
• Containerization: Official Docker images are maintained on GitHub Container Registry. The container exposes the game port and mounts a persistent volume for map archives and logs, enabling quick spin‑up of dedicated servers in cloud environments.
• Scalability: While each server instance handles a single match, developers can orchestrate multiple instances behind a load balancer or matchmaking service. The deterministic nature of the engine allows for stateless session management, simplifying horizontal scaling.
• High Availability: The game’s stateless client can be distributed via CDN, while servers can be replicated across regions with minimal configuration changes.

• APIs: A RESTful API layer can be added via a lightweight web server (e.g., Express.js or FastAPI) to expose matchmaking, player stats, and configuration endpoints. The engine itself provides a C++ API that can be wrapped in Python or Lua for rapid prototyping.
• Webhooks: Developers may hook into game events (e.g., map completion, victory conditions) to trigger external actions such as Discord notifications or database updates.
• Custom Plugins: By implementing the IPlugin interface, developers can inject new components into the engine’s update loop. This is commonly used for custom AI modules or analytics collectors.
• Modding Tools: The community provides a set of CLI tools (0ad-make, 0ad-modpack) that compile map archives, validate assets, and package mods for distribution.

• Configuration: All server settings are exposed via a single server.cfg file, supporting environment variables and command‑line overrides. This makes CI/CD pipelines straightforward.
• Documentation: The official documentation is hosted on GitHub Pages and includes a comprehensive developer guide, API reference, and modding tutorials. The source code is heavily commented, aiding new contributors.
• Community Support: An active mailing list, Discord channel, and IRC room provide real‑time assistance. The project follows a meritocratic contribution model with clear guidelines for pull requests and issue triage.
• Licensing: GPLv2 ensures that any derivative work must remain open source, which aligns with many institutional policies and encourages transparency.

• Academic Research: The deterministic engine is ideal for studying multi‑agent systems, real‑time decision making, and networked simulation.
• Competitive Esports: Hosting private tournaments or community leagues without relying on third‑party servers.
• Enterprise Training: Simulating resource management and strategy scenarios for business or military training programs.
• IoT & Edge Computing: Running lightweight servers on edge devices to provide low‑latency multiplayer in remote locations.

• Performance: Native C++ engine