OpenTomb or OpenLara (classic Tomb Raider 1-5) reverse engineered open-source engine as a libretro core could maybe be nice?
OpenTomb – Cross-platform C++ open source engine for OpenGL
http://opentomb.github.io/
https://github.com/opentomb/OpenTomb
OpenLara – Cross-platform C++ open source engine for WebGL
http://xproger.info/projects/OpenLara/
https://github.com/XProger/OpenLara