Open-source alternatives to Source Sdk 2013

Openage is an open-source game engine designed to execute real-time strategy games. It provides the core logic, networking, and rendering infrastructure necessary to recreate classic strategy mechanics across multiple operating systems. The engine utilizes a deterministic lockstep simulation and a client-server architecture to maintain synchronized game states across participants. It distinguishes itself through a data-driven configuration system that allows for extensive game modding, enabling users to adjust mechanics and visual elements by editing human-readable files without requiring sou

Piccolo is a mini game engine designed for building small-scale games with cross-platform support. It compiles and runs on Windows, macOS, and Linux from a unified codebase, and includes an editor integration for live editing and debugging. The engine uses a component-based entity system with data-oriented design, storing component data in contiguous arrays for cache-friendly iteration. It features a fixed timestep game loop that decouples simulation updates from rendering frame rate, and provides a physics debug overlay that renders visual shapes from simulation data synchronized with the ed

Space Station 14 is a C# multiplayer game and roleplay simulation framework. It is built upon an Entity-Component-System (ECS) game engine that separates logic into systems and data into components to manage complex entity interactions. The project functions as a grid-based physics simulator with a YAML data-driven prototype system for defining game objects. The project features a specialized 2D sprite rendering engine that maps server-side appearance data to client-side shaders. It implements a networking model with client-side prediction and dirty-flagged state synchronization to reduce inp

This repository is a collection of reference implementations and sample projects demonstrating data-oriented design using the Unity Entities package. It provides a suite of examples for implementing an entity component system that separates game data into components and logic into systems. The collection includes specialized demonstrations for rendering large volumes of entities via graphics pipelines, implementing high-performance collision and rigid body dynamics through data-oriented physics, and managing multiplayer state synchronization using the network framework for entities. It also p

OpenDiablo2 is an open-source re-implementation of an isometric action role-playing game engine. It functions as a cross-platform game client designed to execute core mechanics and logic across multiple operating systems using external game assets. The project focuses on recreating the functionality of a classic action RPG from the ground up through a community-driven effort. It provides a framework for running a game engine that simulates specific gameplay experiences and movement patterns. The engine includes capabilities for isometric projection rendering, deterministic game state simulat

Bevy is a cross-platform game engine and framework built in Rust, designed for creating interactive simulations and graphical applications. It utilizes a data-oriented entity-component-system architecture to manage game state, organizing data into contiguous memory blocks to facilitate high-performance processing and massive parallelization of entities. The engine distinguishes itself through a modular plugin architecture and a system-based task scheduler that automatically parallelizes logic by analyzing data access patterns. By employing reactive change detection and deferred command buffer

Endless Sky is an open-source space trading simulation, 2D space combat simulator, and narrative exploration game. It functions as a plugin-based game engine that allows users to explore a vast universe, engage in tactical ship battles, and progress through a central plot within a sandbox environment. The project is distinguished by its highly moddable architecture, utilizing a directory-based plugin system and data-driven entity definitions to allow for content extensions and behavior overrides without recompiling source code. It further supports visual customization through programmable ver

OpenTTD is an open-source game engine and transport simulation game. It provides an isometric sandbox environment for building and managing complex logistics and transport networks. The project functions as a multiplayer simulation sandbox where users can build infrastructure cooperatively or competitively in a shared virtual world. The platform is designed as a moddable simulation system that supports external assets, graphics, and gameplay modifications. It includes mechanisms for downloading and integrating add-on content and utilizes a plugin-based system to extend game mechanics beyond t

Battle for Wesnoth is an open-source turn-based strategy game set in a high fantasy world, built around hex-grid tactical combat. At its core, it is both a complete game and a game engine, offering single-player campaigns and multiplayer battles where players command faction-specific units across terrain that provides tactical advantages. The project is fundamentally a turn-based strategy game with a dedicated multiplayer platform, supporting online and local matches with replay recording and playback. What distinguishes Wesnoth is its deep commitment to custom content creation and modding. T

OpenLara is an open-source game engine and classic game emulator designed to load and execute original game data files from classic action-adventure titles. It functions as a cross-platform game runtime that enables legacy game assets to run on modern hardware and operating systems. The engine features a deterministic physics system using fixed-point coordinate math to ensure consistent movement and behavior across different hardware environments. The project incorporates a component-based entity system and a data-driven level loading process to reconstruct world geometry and object placemen

This repository contains the C++ game source code for a single-player first-person shooter action game. It is a software implementation of the Id Tech 4 engine, designed for 3D rendering with a focus on real-time unified lighting and geometry. The project enables the modification of core engine logic and rendering systems. It serves as a resource for classic game engine modification, first-person shooter development, and retro game preservation. The engine utilizes a unified shader pipeline and stencil shadow volumes for lighting effects, alongside BSP tree spatial partitioning for visibilit

TrinityCore is an open-source game backend and MMORPG game server emulator. It is implemented as a C++ game engine designed to handle real-time network traffic and game state synchronization, utilizing a MySQL database schema to store player profiles, inventories, and world state. The project provides the infrastructure necessary for MMORPG server hosting and private game server administration. It includes tools for game world customization, allowing for the modification of game mechanics, item statistics, and quest scripts. The system manages virtual world infrastructure through multi-threa

This repository provides the source code for the Unity game engine, serving as a reference for the internal implementation of its core systems and managed scripting environment. It functions as a development resource for understanding how high-level C# logic interacts with the underlying engine architecture to build interactive 2D and 3D applications. By providing visibility into the engine's source files, this project enables developers to inspect execution flows and trace implementation details. This transparency supports the troubleshooting of complex behaviors and the analysis of how spec

Hazel is a C++ game development framework and 3D graphics rendering engine designed for building high-performance interactive software. It provides a foundational architecture that enables the construction of desktop applications through native hardware acceleration. The project includes a dedicated game engine editor that allows for the design and testing of interactive 3D and 2D scenes within a unified environment. This editor utilizes an immediate mode interface to maintain synchronization with the engine state, while a hardware-agnostic abstraction layer handles rendering commands across

This is a documentation and sample project for learning Unreal Engine's Gameplay Ability System (GAS), focused on building networked gameplay abilities that synchronize correctly in a multiplayer environment. The project provides a step-by-step guide to implementing GAS, covering the core concepts of defining gameplay mechanics through a data-driven attribute system that separates ability logic from character state management. The documentation explores key architectural patterns for multiplayer ability design, including a predicted-action network model that uses client-side prediction and se

This project is a real-time strategy game and military combat simulator focused on modern warfare. It provides a simulation where players build bases and command military units to achieve tactical objectives and execute combat operations across various global locations. The software functions as a user-generated content platform, featuring a community workshop for creating, uploading, and sharing custom maps. It also includes a narrative-driven single-player campaign consisting of a series of strategic missions. Gameplay involves battling computer-controlled commanders that utilize distinct

This project is an open-source 3D game engine designed for building high-fidelity games, simulations, and cinematic environments. It functions as a robotics simulation platform with native integration for ROS 2 to model robot controllers and sensors. The engine features a multi-threaded Forward+ physically based renderer that supports hardware-accelerated ray tracing and global illumination. The system is built on a modular extension architecture using Gems to add or replace features without modifying core binaries. It includes a native SDK for AWS cloud integration, enabling IAM authenticati

This is a web-based 3D game engine designed for creating high-performance interactive experiences on web and mobile platforms. It functions as a real-time graphics renderer and physics engine, utilizing a component-based scene graph to organize entities and their properties for three-dimensional rendering. The engine includes a visual scene editor that allows for the design of environments through a graphical interface, which then exports these assets as executable code. Its broader capabilities cover real-time graphics rendering for 2D and 3D elements, physical world simulation for object c

Urho3D is a cross-platform 3D game engine written in C++. It uses a component-based scene graph to compose game objects from nodes and attached components, separating transforms from behaviors for modular design. The engine integrates AngelScript and Lua scripting for game logic, uses the Bullet library for physics simulation, and renders scenes with OpenGL or Direct3D through forward, deferred, or light pre-pass pipelines with customizable render passes and shadow mapping. The engine distinguishes itself with a built-in visual scene and UI editor for composing 3D worlds and interface layouts

FXGL is a 2D game engine and development framework designed for Java and Kotlin. It provides a structured environment for building cross-platform desktop games, integrating a central game loop with an entity component system and a JavaFX-based scene graph for rendering. The toolkit distinguishes itself by providing a comprehensive suite of integrated libraries for game AI pathfinding, physics collision resolution, and multiplayer networking via TCP and UDP protocols. It includes specialized systems for adaptive user interface design using global stylesheets and a data-driven asset management

Cocos2d-x is a high-performance C++ game development framework designed for building and deploying interactive applications across mobile, desktop, and web platforms. It functions as a cross-platform game engine that utilizes an entity-component system to manage object lifecycles, behaviors, and spatial relationships within a unified codebase. The engine is distinguished by its specialized 2D graphics rendering pipeline, which is optimized for hardware-accelerated performance when displaying sprites, particle effects, and skeletal animations. It provides developers with low-level access to gr

MonoGame is a cross-platform game framework and C# game engine designed for the development of interactive software. It provides a unified environment for building games that run across desktop, mobile, and console platforms using a single codebase. The framework functions as a 2D graphics rendering library, offering tools to apply custom shaders and visual effects to game assets. It utilizes a graphics abstraction layer to map drawing commands to platform-specific APIs, ensuring consistent rendering across diverse hardware. The engine manages hardware-level tasks such as input handling, aud

Gameplay is a high-performance C++ game engine and cross-platform framework designed for developing 2D and 3D interactive games. It functions as both a 3D graphics engine for rendering environments and a 2D game development kit for creating sprite-based mechanics. The framework provides a cross-platform abstraction layer to ensure that game logic and graphics run across various hardware and software platforms using a shared codebase. The engine implements a hardware-accelerated rendering pipeline and component-based game logic to separate data from behavior. It utilizes a native C++ impleme

Flecs is a high-performance entity component system framework and data-oriented programming library. It serves as a simulation engine core and game engine architecture tool, decoupling state from behavior by separating entities, components, and systems. The framework features a runtime reflection layer for dynamic data inspection and a built-in scripting system for defining entity behavior without recompilation. It also includes a network interface and REST API for remote simulation administration and state querying. The library covers a broad surface of simulation capabilities, including ar

Amethyst is a data-driven game engine written in Rust for building high-performance 2D and 3D games. It is built on an entity component system architecture that decouples game state from logic to enable parallel processing and reusable code. The framework features a glTF 3D renderer for importing scenes and geometry using physically based materials. It also serves as a multiplayer game framework, providing network transport abstractions and state synchronization for real-time online experiences. The engine covers a broad range of capabilities, including hybrid 2D/3D rendering, asynchronous a

This repository contains the original source code for a classic real-time strategy game, serving as a legacy game engine implementation for managing units, maps, and combat mechanics in a military strategy setting. It functions as a real-time strategy game source code archive intended for preservation and technical study. The codebase acts as a game modification base, allowing developers to create custom content and modifications using the original source. It provides a foundation for retro game modding and software archeology to analyze how historical game mechanics were programmed. The pro

This project is an open-source, cross-platform rhythm game engine designed to execute musical gameplay by synchronizing visual hit objects with audio tracks. It functions as a comprehensive competitive gaming platform that tracks player performance metrics, manages official leaderboards, and facilitates the distribution of rhythm-based challenges across desktop and mobile operating systems. The engine distinguishes itself through a modular architecture that decouples core gameplay logic from the engine, allowing developers to implement distinct game modes as swappable rulesets. It includes a