The Open Toolkit library is a fast, low-level C# wrapper for OpenGL
dhewm 3 main repository
Orx: Portable Game Engine
GemRB is a portable open-source implementation of the Infinity Engine
Modified source engine (2017) developed by valve and leaked in 2020
DOOM / Heretic / Hexen source port with enhanced graphics and UI
Improved version of the X-Ray Engine, the game engine
Low-Level Game Engine for Retro Platforms
Portable game engine with main focus on point-and-click adventures
scriptable game engine with built-in support for 2D graphics and sound
Multi-platform game engine similar to old Megaman with a stage editor
Paintown is a 2d fighting game engine.
A generic 2D engine for any kind of game
Point-and-click 2D game engine