A high-performance, industry-standard 2D physics engine built on Box2D
2D JavaScript Physics Engine
A completely free, open-source, 2D game engine
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
Cross-Platform C++ 2D/3D game engine
A cross platform Lua based game engine
Modern AS3 Game Engine
2D physics engine for games
A libgdx pinball game.
A cross-platform OpenGL based lightweight scenegraph library
Box2d Flash Alchemy Port + World Construction Kit