Glad that you got it to run and that you enjoyed it. The engine is a C++ programme that embeds the Duktape Javascript library and provides rendering to either Direct3D8 or OpenGL.
Viewing post in Intern's First Day jam comments
I hadn't heard of Groovy before, that looks cool.
The C++ side of things handles graphics (sprites, backgrounds, fonts), sound, pathfinding, converting input into events for the script, and file IO and has a rudimentary GUI layer, the Javascript side of things uses those APIs and classes as they are exposed from C++. Most of the typical adventure game stuff (the game UI, inventory management, cutscenes, loading/saving, responding to keyboard/mouse events) is handled entirely in Javascript, usually as modules that I import into new projects as needed. No changes were made to the language itself, as that is all just vanilla Javascript.