FYI, this game uses the free https://github.com/thinlizzy/die-tk engine which is a simple toolkit to handle windows and graphics in a portable way.
Other opensource libraries used were https://github.com/thinlizzy/libimage , https://github.com/thinlizzy/libjukebox and the great https://github.com/ThePhD/sol2 which handles the Lua scripts.