It wasn't coded in Quest, although there is a small amount of overlap - there's a C# version of Quest's text processor in there, for example.
The script itself is written using a modified version of the format I'm developing for a new project called Squiffy, which is a simple compiler for multiple choice interactive fiction - see
https://github.com/textadventures/squiffyThe map is rendered using PaperJS - see
http://paperjs.org/ - this is the same library that Quest uses for displaying its map, so the experience there was certainly useful.