Polycode is a free, open-source, cross-platform framework for creative code. You can use it as a C++ API or as a standalone scripting language to get easy and simple access to accelerated 2D and 3D graphics, hardware shaders, sound and network programming, physics engines and more.
The core Polycode API is written in C++ and can be used to create portable native applications.
On top of the core C++ API, Polycode offers a Lua-based scripting system with its own set of compilation tools. The Lua API mirrors the C++ API and can be used to easily create prototypes and even publish complete applications to multiple platforms without compiling C++.
Funny is that I knew Polycode and Bitworld roguelike but never suspected that the game was written on that. I quickly checked OSX app contents of the game and appears be compiled/contained in a kind of standalone player. But there is the C++ and the Lua flavor. It's Lua version compiled too or that only happens in C++ version? If it's so I it's a rare case. Someday I will check and test Polycode potential.