I'm so glad it's made such an impression! This has absolutely made my day. :-)
The game was made with Twine, which I'm a huge fan of: it's really simple to pick up and use, but offers a lot of power and flexibility despite that. I've actually written a series of tutorials on it, and if you're curious how this particular game fits together you can actually import the HTML file back into Twine and explore its flowchart by following this one. (It might be a little hard to follow exactly how it works if you're unfamiliar with Twine, but the basic structure should be easy enough to grasp.)