Kami 2D is a flexible 2D networked multiplayer game engine which I created to provide common features necessary for several game ideas which I wanted to explore. The first and foremost game made in the engine is Blade Flux, which was co-developed with the engine.
The engine is written in C++, game objects are scripted in Lua. The main functionality provided is the automatic networking of physics objects using a custom written networking system. The engine itself is very flexible, and can be used to create virtually any kind of 2D game without touching the actual game engine code, or even recompiling.
Several open source projects are used to provide various functionality for the engine, including SFML (2D rendering and multimedia), Box2d (physics), Lua and Luabind (object scripting), Chromium Embedded Framework (webpage rendering for menus), and others.