Chateau Gaillard was a BASIC program that I copied out of the late Tim Hartnell's book Creating Adventure Games on Your Computer, and accounts for my first experience with computer programming in the late 1980s. I came back to this in 2013 partially out of nostalgia, but more importantly because I had learned of Hartnell's death and wanted to do something to memorialize his contribution to the learning of programming procedures to countless children and teenagers. Without Hartnell's clear instruction, and his focus on making the topic entertaining, I don't think I would have learned how to code in general, and perhaps would not have even had the pre-requisite knowledge to understand something as simple as HTML.
I really cannot overemphasize the profound effect this book had on my childhood. Please do give the game a visit by clicking the image below.